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The CN Tower (french: Tour CN) is a
concrete Concrete is a composite material composed of fine and coarse aggregate bonded together with a fluid cement (cement paste) that hardens (cures) over time. Concrete is the second-most-used substance in the world after water, and is the most wid ...
communications and observation
tower A tower is a tall structure, taller than it is wide, often by a significant factor. Towers are distinguished from masts by their lack of guy-wires and are therefore, along with tall buildings, self-supporting structures. Towers are specific ...
in
downtown Toronto Downtown Toronto is the main central business district of Toronto, Ontario, Canada. Located entirely within the district of Old Toronto, it is approximately 16.6 square kilometres in area, bounded by Bloor Street to the northeast and Dupont Str ...
,
Ontario Ontario ( ; ) is one of the thirteen provinces and territories of Canada.Ontario is located in the geographic eastern half of Canada, but it has historically and politically been considered to be part of Central Canada. Located in Central Ca ...
, Canada. Built on the former
Railway Lands Railway Lands is an area in Downtown Toronto, Ontario, Canada. Originally a large railway switching yard near the Toronto waterfront, including the CNR Spadina Roundhouse and the CPR John Roundhouse, it has since been redeveloped and today is hom ...
, it was completed in 1976. Its name "CN" referred to
Canadian National The Canadian National Railway Company (french: Compagnie des chemins de fer nationaux du Canada) is a Canadian Class I freight railway headquartered in Montreal, Quebec, which serves Canada and the Midwestern and Southern United States. CN ...
, the railway company that built the tower. Following the railway's decision to divest non-core freight railway assets prior to the company's
privatization Privatization (also privatisation in British English) can mean several different things, most commonly referring to moving something from the public sector into the private sector. It is also sometimes used as a synonym for deregulation when ...
in 1995, it transferred the tower to the Canada Lands Company, a federal
Crown corporation A state-owned enterprise (SOE) is a government entity which is established or nationalised by the ''national government'' or ''provincial government'' by an executive order or an act of legislation in order to earn profit for the government ...
responsible for real estate development. The CN Tower held the record for the world's tallest free-standing structure for 32 years, from 1975 until 2007, when it was surpassed by the
Burj Khalifa The Burj Khalifa (; ar, برج خليفة, , Khalifa Tower), known as the Burj Dubai prior to its inauguration in 2010, is a skyscraper in Dubai, United Arab Emirates. It is known for being the world’s tallest building. With a total height ...
, and was the world's tallest tower until 2009 when it was surpassed by the Canton Tower. It is currently the ninth-tallest free-standing structure in the world and remains the tallest free-standing structure on land in the
Western Hemisphere The Western Hemisphere is the half of the planet Earth that lies west of the prime meridian (which crosses Greenwich, London, United Kingdom) and east of the antimeridian. The other half is called the Eastern Hemisphere. Politically, the te ...
. In 1995, the CN Tower was declared one of the modern Seven
Wonders of the World Various lists of the Wonders of the World have been compiled from antiquity to the present day, in order to catalogue the world's most spectacular natural features and human-built structures. The Seven Wonders of the Ancient World is the o ...
by the
American Society of Civil Engineers American(s) may refer to: * American, something of, from, or related to the United States of America, commonly known as the "United States" or "America" ** Americans, citizens and nationals of the United States of America ** American ancestry, p ...
. It also belongs to the World Federation of Great Towers. It is a signature icon of Toronto's
skyline A skyline is the outline or shape viewed near the horizon. It can be created by a city’s overall structure, or by human intervention in a rural setting, or in nature that is formed where the sky meets buildings or the land. City skylin ...
and attracts more than two million international visitors annually. It houses several observation decks, a revolving restaurant at some , and an entertainment complex.


History

The original concept of the CN Tower was first conceived in 1968 when the
Canadian National Railway The Canadian National Railway Company (french: Compagnie des chemins de fer nationaux du Canada) is a Canadian Class I freight railway headquartered in Montreal, Quebec, which serves Canada and the Midwestern and Southern United States. CN i ...
wanted to build a large television and radio communication platform to serve the Toronto area, and to demonstrate the strength of Canadian industry and CN in particular. These plans evolved over the next few years, and the project became official in 1972. The tower would have been part of Metro Centre (see CityPlace), a large development south of Front Street on the
Railway Lands Railway Lands is an area in Downtown Toronto, Ontario, Canada. Originally a large railway switching yard near the Toronto waterfront, including the CNR Spadina Roundhouse and the CPR John Roundhouse, it has since been redeveloped and today is hom ...
, a large railway switching yard that was being made redundant after the opening of the
MacMillan Yard The MacMillan Yard is the 2nd largest rail classification yard in Canada, after CN's Symington Yard in Winnipeg. It is operated by Canadian National Railway (CN) and is located in Vaughan, Ontario. It was originally opened in 1965 as Toronto Yar ...
north of the city in 1965 (then known as Toronto Yard). Key project team members were NCK Engineering as structural engineer; John Andrews Architects; Webb, Zerafa, Menkes, Housden Architects; Foundation Building Construction; and Canron (Eastern Structural Division). As Toronto grew rapidly during the late 1960s and early 1970s, multiple skyscrapers were constructed in the downtown core, most notably
First Canadian Place First Canadian Place (originally First Bank Building) is a skyscraper in the Financial District of Toronto, Ontario, at the northwest corner of King and Bay streets, and serves as the global operational headquarters of the Bank of Montreal. A ...
. The reflective nature of the new buildings reduced the quality of broadcast signals, requiring new, higher antennas that were at least tall. The radio wire is estimated to be 102 meters long in 44 pieces - the heaviest of which weighs around eight tons. At the time, most data communications took place over point-to-point microwave links, whose dish antennae covered the roofs of large buildings. As each new skyscraper was added to the downtown, former line-of-sight links were no longer possible. CN intended to rent "hub" space for microwave links, visible from almost any building in the Toronto area. The original plan for the tower envisioned a tripod consisting of three independent cylindrical "pillars" linked at various heights by structural bridges. Had it been built, this design would have been considerably shorter, with the metal antenna located roughly where the concrete section between the main level and the SkyPod lies today. As the design effort continued, it evolved into the current design with a single continuous hexagonal core to the SkyPod, with three support legs blended into the hexagon below the main level, forming a large Y-shape structure at the ground level. The idea for the main level in its current form evolved around this time, but the Space Deck (later renamed SkyPod) was not part of the plans until some time later. One engineer, in particular, felt that visitors would feel the higher observation deck would be worth paying extra for, and the costs in terms of construction were not prohibitive. It was also some time around this point that it was realized that the tower could become the world's tallest free-standing structure to improve signal quality and attract tourists, and plans were changed to incorporate subtle modifications throughout the structure to this end.


Construction

The CN Tower was built by Canada Cement Company (also known as the Cement Foundation Company of Canada at the time), a subsidiary of Sweden's
Skanska Skanska AB () is a multinational construction and development company based in Sweden. Skanska is the fifth-largest construction company in the world according to ''Construction Global'' magazine. Notable Skanska projects include renovation of t ...
, a global project-development and construction group. Construction began on February 6, 1973, with massive excavations at the tower base for the foundation. By the time the foundation was complete, of
earth Earth is the third planet from the Sun and the only astronomical object known to harbor life. While large volumes of water can be found throughout the Solar System, only Earth sustains liquid surface water. About 71% of Earth's sur ...
and
shale Shale is a fine-grained, clastic sedimentary rock formed from mud that is a mix of flakes of clay minerals (hydrous aluminium phyllosilicates, e.g. kaolin, Al2 Si2 O5( OH)4) and tiny fragments (silt-sized particles) of other minerals, especiall ...
were removed to a depth of in the centre, and a base incorporating of concrete with of
rebar Rebar (short for reinforcing bar), known when massed as reinforcing steel or reinforcement steel, is a steel bar used as a tension device in reinforced concrete and reinforced masonry structures to strengthen and aid the concrete under tension. ...
and of
steel cable Steel wire rope (right hand lang lay) Wire rope is several strands of metal wire twisted into a helix forming a composite ''rope'', in a pattern known as ''laid rope''. Larger diameter wire rope consists of multiple strands of such laid rope in a ...
had been built to a thickness of . This portion of the construction was fairly rapid, with only four months needed between the start and the foundation being ready for construction on top. To create the main support pillar, workers constructed a hydraulically raised
slipform Slip forming, continuous poured, continuously formed, or slipform construction is a construction method in which concrete is poured into a continuously moving form.Nawy, ''Concrete Construction Engineering Handbook,'' 2008, p. 10—33. Slip form ...
at the base. This was a fairly unprecedented engineering feat on its own, consisting of a large metal platform that raised itself on jacks at about per day as the concrete below set. Concrete was poured Monday to Friday (not continuously) by a small team of people until February 22, 1974, at which time it had already become the tallest structure in Canada, surpassing the recently built
Inco Superstack The Inco Superstack in Sudbury, Ontario, with a height of , is the tallest chimney in Canada and the Western hemisphere, and the second tallest freestanding chimney in the world after the GRES-2 Power Station in Kazakhstan. It is also the s ...
in
Sudbury Sudbury may refer to: Places Australia * Sudbury Reef, Queensland Canada * Greater Sudbury, Ontario (official name; the city continues to be known simply as Sudbury for most purposes) ** Sudbury (electoral district), one of the city's federal el ...
, which was built using similar methods. The tower contains of concrete, all of which was mixed on-site in order to ensure batch consistency. Through the pour, the vertical accuracy of the tower was maintained by comparing the slip form's location to massive
plumb bob A plumb bob, plumb bob level, or plummet, is a weight, usually with a pointed tip on the bottom, suspended from a string and used as a vertical reference line, or plumb-line. It is a precursor to the spirit level and used to establish a verti ...
s hanging from it, observed by small telescopes from the ground. Over the height of the tower, it varies from true vertical accuracy by only . In August 1974, construction of the main level commenced. Using 45 hydraulic jacks attached to cables strung from a temporary steel crown anchored to the top of the tower, twelve giant steel and wooden bracket forms were slowly raised, ultimately taking about a week to crawl up to their final position. These forms were used to create the brackets that support the main level, as well as a base for the construction of the main level itself. The Space Deck (currently named SkyPod) was built of concrete poured into a wooden frame attached to rebar at the lower level deck, and then reinforced with a large steel compression band around the outside. While still under construction, the CN Tower officially became the world's tallest free-standing structure on March 31, 1975. The antenna was originally to be raised by crane as well, but during construction, the
Sikorsky S-64 Skycrane The Sikorsky S-64 Skycrane is an American twin-engine heavy-lift helicopter. It is the civil version of the United States Army's CH-54 Tarhe. It is currently produced as the S-64 Aircrane by Erickson Inc. Development Under Sikorsky ...
helicopter became available when the
United States Army The United States Army (USA) is the land service branch of the United States Armed Forces. It is one of the eight U.S. uniformed services, and is designated as the Army of the United States in the U.S. Constitution.Article II, section 2, ...
sold one to civilian operators. The helicopter, named "Olga", was first used to remove the crane, and then flew the antenna up in 36 sections. The flights of the antenna pieces were a minor tourist attraction of their own, and the schedule was printed in the local newspapers. Use of the helicopter saved months of construction time, with this phase taking only three and a half weeks instead of the planned six months. The tower was topped-off on April 2, 1975, after 26 months of construction, officially capturing the height record from
Moscow Moscow ( , US chiefly ; rus, links=no, Москва, r=Moskva, p=mɐskˈva, a=Москва.ogg) is the capital and largest city of Russia. The city stands on the Moskva River in Central Russia, with a population estimated at 13.0 million ...
's
Ostankino Tower Ostankino Tower (russian: links=no, Останкинская телебашня, Ostankinskaya telebashnya) is a television and radio tower in Moscow, Russia, owned by the Moscow branch of unitary enterprise Russian TV and Radio Broadcasting Ne ...
, and bringing the total mass to . Two years into the construction, plans for Metro Centre were scrapped, leaving the tower isolated on the Railway Lands in what was then a largely abandoned light-industrial space. This caused serious problems for tourists to access the tower. Ned Baldwin, project architect with John Andrews, wrote at the time that "All of the logic which dictated the design of the lower accommodation has been upset," and that "Under such ludicrous circumstances Canadian National would hardly have chosen this location to build."


Phases of construction

File:CN Tower footings 1973.jpg, Constructing the base, July 1973 File:Cntower1974.jpg, Brackets being raised, August 1974 File:CN Tower50 construction skycrane March 1975 01d.jpg, Helicopter lifting part of antenna, March 1975 File:CN Tower under construction (April 1975).jpg, Main pod construction, April 1975 File:CN Tower under construction.jpg, Nearing completion, December 1975 File:CN Tower 1976.jpg, Two months after opening, August 1976


Opening

The CN Tower opened on June 26, 1976. The construction costs of approximately ($ in dollars) were repaid in fifteen years. From the mid-1970s to the mid-1980s, the CN Tower was practically the only development along Front Street West; it was still possible to see Lake Ontario from the foot of the CN Tower due to the expansive parking lots and lack of development in the area at the time. As the area around the tower was developed, particularly with the completion of the
Metro Toronto Convention Centre Metro Toronto Convention Centre (originally and still colloquially Metro Convention Centre, and sometimes MTCC), is a convention complex located in Toronto, Ontario, Canada along Front Street West in the former Railway Lands in downtown Toronto. ...
(north building) in 1984 and SkyDome in 1989 (renamed
Rogers Centre Rogers Centre (originally SkyDome) is a multi-purpose retractable roof stadium in Downtown Toronto, Ontario, Canada, situated at the base of the CN Tower near the northern shore of Lake Ontario. Opened in 1989 on the former Railway Lands, ...
in 2005), the former
Railway Lands Railway Lands is an area in Downtown Toronto, Ontario, Canada. Originally a large railway switching yard near the Toronto waterfront, including the CNR Spadina Roundhouse and the CPR John Roundhouse, it has since been redeveloped and today is hom ...
were redeveloped and the tower became the centre of a newly developing entertainment area. Access was greatly improved with the construction of the
SkyWalk A skyway, skybridge, skywalk, or sky walkway is an elevated type of pedway connecting two or more buildings in an urban area, or connecting elevated points within mountainous recreational zones. Urban skyways very often take the form of enclos ...
in 1989, which connected the tower and SkyDome to the nearby Union Station railway and subway station, and, in turn, to the city's Path underground pedestrian system. By the mid-1990s, it was the centre of a thriving tourist district. The entire area continues to be an area of intense building, notably a
boom Boom may refer to: Objects * Boom (containment), a temporary floating barrier used to contain an oil spill * Boom (navigational barrier), an obstacle used to control or block marine navigation * Boom (sailing), a sailboat part * Boom (windsurfin ...
in
condominium A condominium (or condo for short) is an ownership structure whereby a building is divided into several units that are each separately owned, surrounded by common areas that are jointly owned. The term can be applied to the building or complex ...
construction in the first quarter of the 21st century, as well as the 2013 opening of the
Ripley's Aquarium Ripley Entertainment Inc. is an entertainment and edutainment holding company owned by the Jim Pattison Group of Vancouver, British Columbia, Canada. The company has its headquarters in an unincorporated Unincorporated may refer to: * Unincorpora ...
by the base of the tower.


Early years

When the CN Tower opened in 1976, there were three public observation points: the SkyPod (then known as the Space Deck) that stands at , the Indoor Observation Level (later named Indoor Lookout Level) at , and the Outdoor Observation Terrace (at the same level as the Glass Floor) at . One floor above the Indoor Observation Level was the Top of Toronto Restaurant, which completed a revolution once every 72 minutes. The tower would garner worldwide media attention when stuntman Dar Robinson jumped off of the CN Tower on two occasions in 1979 and 1980. The first was for a scene from the movie ''
Highpoint Highpoint can refer to: * Highpoint, Florida, an unincorporated community near Tampa Bay *Highpoint Shopping Centre in Melbourne, Australia *Highpoint (building), an apartment building in London, United Kingdom. *Highpoint I, a set of 1930s apartme ...
'', in which Robinson received $250,000 ($ in dollars) for the stunt. The second was for a personal documentary. Both stunts used a wire decelerator attached to his back as a safety measure. On June 26, 1986, the ten-year anniversary of the tower's opening, high-rise firefighting and rescue advocate Dan Goodwin, in a sponsored publicity event, used his hands and feet to climb the outside of the tower, a feat he performed twice on the same day. Following both ascents, he used multiple rappels to descend to the ground.


The 1990s and 2000s

A glass floor at an elevation of was installed in 1994. Canadian National Railway sold the tower to Canada Lands Company prior to privatizing the company in 1995, when it divested all operations not directly related to its core freight shipping businesses. The tower's name and wordmark were adjusted to remove the CN railways logo, and the tower was renamed Canada's National Tower (from Canadian National Tower), though the tower is commonly called the CN Tower. Further changes were made from 1997 to January 2004, TrizecHahn Corporation managed the tower and instituted several expansion projects including a entertainment expansion and revitalization that included the 1997 addition of two new elevators (to a total of six) and the consequential relocation of the staircase from the north side leg to inside the core of the building, a conversion that also added nine stairs to the climb. TrizecHahn also owned the
Willis Tower The Willis Tower (originally the Sears Tower) is a 108- story, skyscraper in the Loop community area of Chicago in Illinois, United States. Designed by architect Bruce Graham and engineer Fazlur Rahman Khan of Skidmore, Owings & Merrill (SOM ...
(Sears Tower at the time) in Chicago approximately at the same time. In 2007,
light-emitting diode A light-emitting diode (LED) is a semiconductor Electronics, device that Light#Light sources, emits light when Electric current, current flows through it. Electrons in the semiconductor recombine with electron holes, releasing energy i ...
(LED) lights replaced the incandescent lights that lit the CN Tower at night, the reason cited being that LED lights are more cost and energy efficient than the incandescent lights. The colour of the LED lights can change, compared to the constant white colour of the incandescent lights. On September 12, 2007,
Burj Khalifa The Burj Khalifa (; ar, برج خليفة, , Khalifa Tower), known as the Burj Dubai prior to its inauguration in 2010, is a skyscraper in Dubai, United Arab Emirates. It is known for being the world’s tallest building. With a total height ...
, then under construction and known as Burj Dubai, surpassed the CN Tower as the world's tallest free-standing structure. In 2008, glass panels were installed in one of the CN Tower elevators, which established a world record (346 m) for highest glass floor panelled elevator in the world.


2010s: EdgeWalk

On August 1, 2011, the CN Tower opened the EdgeWalk, an amusement in which thrill-seekers can walk on and around the roof of the main pod of the tower at , which is directly above the 360 Restaurant. It is the world's highest full-circle, hands-free walk. Visitors are tethered to an overhead rail system and walk around the edge of the CN Tower's main pod above the 360 Restaurant on a metal floor. The attraction is closed throughout the winter and during periods of electrical storms and high winds. One of the notable guests who visited EdgeWalk was Canadian comedian
Rick Mercer Richard Vincent "Rick" Mercer (born October 17, 1969) is a Canadian comedian, television personality, political satirist, and author. He is best known for his work on the CBC Television comedy shows '' This Hour Has 22 Minutes'' and ''Rick Merc ...
as featured as the first episode of the ninth season of his
CBC Television CBC Television (also known as CBC TV) is a Canadian English-language broadcast television network owned by the Canadian Broadcasting Corporation, the national public broadcaster. The network began operations on September 6, 1952. Its French- ...
news satire show, ''
Rick Mercer Report ''Rick Mercer Report'' (also called the ''Mercer Report'' or ''RMR'') is a Canadian television comedy series which aired on CBC Television from 2004 to 2018. Launched in 2004, as ''Rick Mercer's Monday Report'', or simply ''Monday Report'', by ...
''. There, he was accompanied by Canadian pop singer
Jann Arden Jann Arden (born Jann Arden Anne Richards; March 27, 1962) is a Canadian singer-songwriter and actress. She is famous for her signature ballads, " Could I Be Your Girl" and " Insensitive", which is her biggest hit to date. Early life and educa ...
. The episode first aired on April 10, 2013.


Pan Am Games

The tower and surrounding areas were prominent in the
2015 Pan American Games Fifteen or 15 may refer to: *15 (number), the natural number following 14 and preceding 16 *one of the years 15 BC, AD 15, 1915, 2015 Music * Fifteen (band), a punk rock band Albums * ''15'' (Buckcherry album), 2005 * ''15'' (Ani Lorak al ...
production. In the opening ceremony a pre-recorded segment featured track-and-field athlete Bruny Surin passing the flame to sprinter Donovan Bailey on the EdgeWalk and parachuting into Rogers Centre. A fireworks display off the tower concluded both the opening and closing ceremonies.


Canada 150

On July 1, 2017, as part of the nationwide celebrations for Canada 150, which celebrated the 150th anniversary of
Canadian Confederation Canadian Confederation (french: Confédération canadienne, link=no) was the process by which three British North American provinces, the Province of Canada, Nova Scotia, and New Brunswick, were united into one federation called the Dominio ...
, fireworks were once again shot from the tower in a five-minute display coordinated with the tower lights and music broadcast on a local radio station.


Closures

*The CN Tower was closed during the
G20 summit The following list of G20 summits summarizes all G20 conferences held at various different levels: summits of heads of state or heads of government, ministerial-level meetings, Engagement Group meetings and others. Summits of state leaders ...
on June 26–27, 2010, for security reasons, given its proximity to the Metro Toronto Convention Centre and ongoing citywide protests and riots. *The CN Tower was closed from 2020 to 2021 due to
COVID-19 pandemic The COVID-19 pandemic, also known as the coronavirus pandemic, is an ongoing global pandemic of coronavirus disease 2019 (COVID-19) caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The novel virus was first identi ...
restrictions in Ontario. *The CN Tower was closed on December 16, 2021, due to glass falling off from heavy winds.


Structure

The CN Tower consists of several substructures. The main portion of the tower is a hollow concrete hexagonal pillar containing the stairwells and power and plumbing connections. The tower's six
elevator An elevator or lift is a cable-assisted, hydraulic cylinder-assisted, or roller-track assisted machine that vertically transports people or freight between floors, levels, or decks of a building, vessel, or other structure. They ...
s are located in the three inverted angles created by the Tower's hexagonal shape (two elevators per angle). Each of the three elevator shafts is lined with glass, allowing for views of the city as the glass-windowed elevators make their way through the tower. The stairwell was originally located in one of these angles (the one facing north), but was moved into the central hollow of the tower; the tower's new fifth and sixth elevators were placed in the hexagonal angle that once contained the stairwell. On top of the main concrete portion of the tower is a tall metal broadcast antenna, carrying television and radio signals. There are three visitor areas: the Glass Floor and Outdoor Observation Terrace, which are both located at an elevation of , the Indoor Lookout Level (formerly known as "Indoor Observation Level") located at , and the higher SkyPod (formerly known as "Space Deck") at , just below the metal
antenna Antenna ( antennas or antennae) may refer to: Science and engineering * Antenna (radio), also known as an aerial, a transducer designed to transmit or receive electromagnetic (e.g., TV or radio) waves * Antennae Galaxies, the name of two collid ...
. The hexagonal shape is visible between the two areas; however, below the main deck, three large supporting legs give the tower the appearance of a large
tripod A tripod is a portable three-legged frame or stand, used as a platform for supporting the weight and maintaining the stability of some other object. The three-legged (triangular stance) design provides good stability against gravitational loads ...
. The main deck level has seven storeys, some of which are open to the public. Below the public areas — at — is a large white donut-shaped radome containing the structure's
UHF Ultra high frequency (UHF) is the ITU designation for radio frequencies in the range between 300 megahertz (MHz) and 3 gigahertz (GHz), also known as the decimetre band as the wavelengths range from one meter to one tenth of a meter (on ...
transmitters. The glass floor and outdoor observation deck are at . The glass floor has an area of and can withstand a pressure of . The floor's thermal glass units are thick, consisting of a pane of laminated glass, airspace and a pane of laminated glass. In 2008, one elevator was upgraded to add a glass floor panel, believed to have the highest vertical rise of any elevator equipped with this feature. The Horizons Cafe and the lookout level are at . The 360 Restaurant, a
revolving restaurant A revolving restaurant or rotating restaurant is usually a tower restaurant eating space designed to rest atop a broad circular revolving platform that operates as a large turntable. The building remains stationary and the diners are carried on ...
that completes a full rotation once every 72 minutes, is at . When the tower first opened, it also featured a disco named Sparkles (at the Indoor Observation Level), billed as the highest disco and dance floor in the world. The SkyPod was once the highest public
observation deck An observation deck, observation platform, or viewing platform is an elevated sightseeing platform usually situated upon a tall architectural structure, such as a skyscraper or observation tower. Observation decks are sometimes enclo ...
in the world until it was surpassed by the Shanghai World Financial Center in 2008. A metal staircase reaches the main deck level after 1,776 steps, and the SkyPod above after 2,579 steps; it is the tallest metal staircase on Earth. These stairs are intended for emergency use only and are not open to the public, except for charity stair-climb events two times during the year. The average climber takes approximately 30 minutes to climb to the base of the radome, but the fastest climb on record is 7 minutes and 52 seconds in 1989 by Brendan Keenoy, an
Ontario Provincial Police The Ontario Provincial Police (OPP) is the provincial police service of Ontario, Canada. Under its provincial mandate, the OPP patrols provincial highways and waterways, protects provincial government buildings and officials, patrols unincorp ...
officer. In 2002, Canadian Olympian and
Paralympic The Paralympic Games or Paralympics, also known as the ''Games of the Paralympiad'', is a periodic series of international multisport events involving athletes with a range of physical disabilities, including impaired muscle power and impaire ...
champion Jeff Adams climbed the stairs of the tower in a specially designed
wheelchair A wheelchair is a chair with wheels, used when walking is difficult or impossible due to illness, injury, problems related to old age, or disability. These can include spinal cord injuries ( paraplegia, hemiplegia, and quadriplegia), ce ...
. The stairs were originally on one of the three sides of the tower (facing north), with a glass view, but these were later replaced with the third elevator pair and the stairs were moved to the inside of the core. Top climbs on the new, windowless stairwell used since around 2003 have generally been over ten minutes. insidecntower360.JPG, Inside 360 Restaurant Toronto - ON - CN Tower Turmkorb.jpg, Main Pod CN Tower Turmkorb-Modell-blau.png, Cross-section of Main Pod CN Tower Glass Floor Walk.jpg, Standing on glass floor CNTowerNastyFall.jpg, View through glass floor


Architects

*
WZMH Architects WZMH Architects is an architectural firm established in 1961 and based in Toronto, Ontario, Canada. Originally known as Webb Zerafa Menkès Housden (after Peter Webb, Boris Zerafa, René Menkès, and Warwick Housden) the company's name was changed t ...
* John Hamilton Andrews *Webb Zerafa *Menkes Housden with the help of E.R. Baldwin


Falling ice danger

A
freezing rain Freezing rain is rain maintained at temperatures below freezing by the ambient air mass that causes freezing on contact with surfaces. Unlike a mixture of rain and snow or ice pellets, freezing rain is made entirely of liquid droplets. The rain ...
storm on March 2, 2007, resulted in a layer of ice several centimetres thick forming on the side of the tower and other downtown buildings. The sun thawed the ice, and winds of up to blew some of it away from the structure. There were fears that cars and windows of nearby buildings would be smashed by large chunks of ice. In response, police closed some streets surrounding the tower. During morning rush hour on March 5 of the same year, police expanded the area of closed streets to include the
Gardiner Expressway The Frederick G. Gardiner Expressway, commonly known as the Gardiner Expressway or simply the Gardiner, is a partially at grade and elevated municipal expressway in Toronto, Ontario, Canada. Running close to the shore of Lake Ontario, it extends ...
away from the tower as increased winds blew the ice farther away, as far north as King Street West, away, where a
taxicab A taxi, also known as a taxicab or simply a cab, is a type of vehicle for hire with a driver, used by a single passenger or small group of passengers, often for a non-shared ride. A taxicab conveys passengers between locations of their choi ...
window was shattered. Subsequently, on March 6, 2007, the Gardiner Expressway reopened after winds abated. On April 16, 2018, falling ice from the CN Tower punctured the roof of the nearby
Rogers Centre Rogers Centre (originally SkyDome) is a multi-purpose retractable roof stadium in Downtown Toronto, Ontario, Canada, situated at the base of the CN Tower near the northern shore of Lake Ontario. Opened in 1989 on the former Railway Lands, ...
stadium, causing the
Toronto Blue Jays The Toronto Blue Jays are a Canadian professional baseball team based in Toronto. The Blue Jays compete in Major League Baseball (MLB) as a member club of the American League (AL) East division. Since 1989, the team has played its home games ...
to postpone the game that day to the following day as a doubleheader; this was the third doubleheader held at the Rogers Centre. On April 20 of the same year, the CN Tower reopened.


Safety features

In August 2000, a fire broke out at the
Ostankino Tower Ostankino Tower (russian: links=no, Останкинская телебашня, Ostankinskaya telebashnya) is a television and radio tower in Moscow, Russia, owned by the Moscow branch of unitary enterprise Russian TV and Radio Broadcasting Ne ...
in
Moscow Moscow ( , US chiefly ; rus, links=no, Москва, r=Moskva, p=mɐskˈva, a=Москва.ogg) is the capital and largest city of Russia. The city stands on the Moskva River in Central Russia, with a population estimated at 13.0 million ...
killing three people and causing extensive damage. The fire was blamed on poor maintenance and outdated equipment. The failure of the fire-suppression systems and the lack of proper equipment for firefighters allowed the fire to destroy most of the interior and spark fears the tower might even collapse. The Ostankino Tower was completed nine years before the CN Tower and is only shorter. The parallels between the towers led to some concern that the CN Tower could be at risk of a similar tragedy. However, Canadian officials subsequently stated that it is "highly unlikely" that a similar disaster could occur at the CN Tower, as it has important safeguards that were not present in the Ostankino Tower. Specifically, officials cited: * the fireproof building materials used in the tower's construction, * frequent and stringent safety inspections, * an extensive sprinkler system, * a 24-hour emergency monitoring operation, * two 68,160-litre (15,000-imperial gallon; 18,006-US gallon) water reservoirs at the top, which are automatically replenished, * a fire hose at the base of the structure capable of sending 2725 litres (600 imperial gallons; 720 US Gallon) a minute to any location in the tower, * a ban on natural gas appliances anywhere in the tower (including the restaurant in the main pod), * an elevator that can be used during a fire as it runs up the outside of the building and can be powered by three emergency generators at the base of the structure (unlike the elevator at the Ostankino Tower, which malfunctioned). Officials also noted that the CN Tower has an excellent safety record, although there was an electrical fire in the antennae on August 16, 2017 — the tower's first fire. Moreover, other supertall structures built between 1967 and 1976 — such as the
Willis Tower The Willis Tower (originally the Sears Tower) is a 108- story, skyscraper in the Loop community area of Chicago in Illinois, United States. Designed by architect Bruce Graham and engineer Fazlur Rahman Khan of Skidmore, Owings & Merrill (SOM ...
(formerly the Sears Tower), the World Trade Center (until its destruction on September 11, 2001), the Fernsehturm Berlin, the Aon Center, 875 North Michigan Avenue (formerly the John Hancock Center), and
First Canadian Place First Canadian Place (originally First Bank Building) is a skyscraper in the Financial District of Toronto, Ontario, at the northwest corner of King and Bay streets, and serves as the global operational headquarters of the Bank of Montreal. A ...
— also have excellent safety records, which suggests that the Ostankino Tower accident was a rare safety failure, and that the likelihood of similar events occurring at other supertall structures is extremely low.


Lighting

The CN Tower was originally lit at night with
incandescent Incandescence is the emission of electromagnetic radiation (including visible light) from a hot body as a result of its high temperature. The term derives from the Latin verb ''incandescere,'' to glow white. A common use of incandescence i ...
lights, which were removed in 1997 because they were inefficient and expensive to repair. In June 2007, the tower was outfitted with 1,330 super-bright LED lights inside the elevator shafts, shooting over the main pod and upward to the top of the tower's mast to light the tower from dusk until 2 a.m. The official opening ceremony took place on June 28, 2007 before the
Canada Day Canada Day (french: Fête du Canada), formerly known as Dominion Day (french: Fête du Dominion), is the national day of Canada. A federal statutory holiday, it celebrates the anniversary of Canadian Confederation which occurred on July 1, 18 ...
holiday weekend. The tower changes its lighting scheme on holidays and to commemorate major events. After the
95th Grey Cup The 95th Grey Cup was held in Toronto at the Rogers Centre on November 25, 2007. The Grey Cup, first awarded in 1909, is the championship game of the Canadian Football League. It was played between the Saskatchewan Roughriders and the Winnip ...
in Toronto, the tower was lit in green and white to represent the colours of the Grey Cup champion Saskatchewan Roughriders. From sundown on August 27, 2011, to sunrise the following day, the tower was lit in orange, the official colour of the
New Democratic Party The New Democratic Party (NDP; french: Nouveau Parti démocratique, NPD) is a federal political party in Canada. Widely described as social democratic,The party is widely described as social democratic: * * * * * * * * * * * * ...
(NDP), to commemorate the
death Death is the irreversible cessation of all biological functions that sustain an organism. For organisms with a brain, death can also be defined as the irreversible cessation of functioning of the whole brain, including brainstem, and brain ...
of federal NDP leader and leader of the official opposition Jack Layton. When former
South African president The president of South Africa is the head of state and head of government of the Republic of South Africa. The president heads the executive branch of the Government of South Africa and is the commander-in-chief of the South African Nation ...
Nelson Mandela Nelson Rolihlahla Mandela (; ; 18 July 1918 – 5 December 2013) was a South African anti-apartheid activist who served as the first president of South Africa from 1994 to 1999. He was the country's first black head of state and the ...
died Death is the irreversible cessation of all biological functions that sustain an organism. For organisms with a brain, death can also be defined as the irreversible cessation of functioning of the whole brain, including brainstem, and brain ...
, the tower was lit in the colours of the
South African flag The flag of South Africa was designed in March 1994 and adopted on 27 April 1994, at the beginning of South Africa's 1994 general election, to replace the flag that had been used since 1928. The flag has horizontal bands of red (on the top) ...
. When former federal finance minister under
Stephen Harper Stephen Joseph Harper (born April 30, 1959) is a Canadian politician who served as the 22nd prime minister of Canada from 2006 to 2015. Harper is the first and only prime minister to come from the modern-day Conservative Party of Canada, ...
's Conservatives Jim Flaherty died, the tower was lit in green to reflect his Irish Canadian heritage. On the night of the attacks on Paris on November 13, 2015, the tower displayed the colours of the French flag. On June 8, 2021, the tower displayed the colours of the
Toronto Maple Leafs The Toronto Maple Leafs (officially the Toronto Maple Leaf Hockey Club and often referred to as the Leafs) are a professional ice hockey team based in Toronto. They compete in the National Hockey League (NHL) as a member of the Atlantic Div ...
' archrivals
Montreal Canadiens The Montreal CanadiensEven in English, the French spelling is always used instead of ''Canadians''. The French spelling of ''Montréal'' is also sometimes used in the English media. (french: link=no, Les Canadiens de Montréal), officially ...
after they advanced to the semifinals of
2021 Stanley Cup playoffs The 2021 Stanley Cup playoffs was the playoff tournament of the National Hockey League (NHL). The playoffs began on May 15, 2021, and concluded on July 7, 2021, with the Tampa Bay Lightning winning their second consecutive and third overall Sta ...
. The CN Tower was lit in the colours of the Ukrainian flag during the beginning of the
2022 Russian invasion of Ukraine On 24 February 2022, in a major escalation of the Russo-Ukrainian War, which began in 2014. The invasion has resulted in tens of thousands of deaths on both sides. It has caused Europe's largest refugee crisis since World War II. A ...
in late February 2022. Programmed remotely from a
desktop computer A desktop computer (often abbreviated desktop) is a personal computer designed for regular use at a single location on or near a desk due to its size and power requirements. The most common configuration has a case that houses the power supply ...
with a wireless network interface controller in
Burlington, Ontario Burlington is a city in the Regional Municipality of Halton at the northwestern end of Lake Ontario in Ontario, Canada. Along with Milton to the north, it forms the western end of the Greater Toronto Area and is also part of the Hamilton m ...
, the LEDs use less energy to light than the previous incandescent lights (10% less energy than the dimly lit version and 60% less than the brightly lit version). The estimated cost to use the LEDs is $1,000 per month. During the spring and autumn
bird migration Bird migration is the regular seasonal movement, often north and south along a flyway, between breeding and wintering grounds. Many species of bird migrate. Migration carries high costs in predation and mortality, including from hunting b ...
seasons, the lights would be turned off to comply with the voluntary Fatal Light Awareness Program, which "encourages buildings to dim unnecessary exterior lighting to mitigate bird mortality during spring and summer migration."


Height comparisons

The CN Tower is the tallest freestanding structure in the Western Hemisphere. As of 2013, there were two other freestanding structures in the Western Hemisphere exceeding in height: the
Willis Tower The Willis Tower (originally the Sears Tower) is a 108- story, skyscraper in the Loop community area of Chicago in Illinois, United States. Designed by architect Bruce Graham and engineer Fazlur Rahman Khan of Skidmore, Owings & Merrill (SOM ...
in Chicago, which stands at when measured to its pinnacle, and One World Trade Center in New York City, which has a pinnacle height of , or approximately shorter than the CN Tower. Due to the symbolism of the number 1776 (the year of the signing of the
United States Declaration of Independence The United States Declaration of Independence, formally The unanimous Declaration of the thirteen States of America, is the pronouncement and founding document adopted by the Second Continental Congress meeting at Pennsylvania State House ( ...
), the height of One World Trade Center is unlikely to be increased. The proposed
Chicago Spire The Chicago Spire was a skyscraper project in Chicago that was partially built between 2007 and 2008 before being cancelled. Located at 400 N. Lake Shore Drive, it would have stood high with 150 floors and been the tallest building in the Weste ...
was expected to exceed the height of the CN Tower, but its construction was halted early due to financial difficulties amid the
Great Recession The Great Recession was a period of marked general decline, i.e. a recession, observed in national economies globally that occurred from late 2007 into 2009. The scale and timing of the recession varied from country to country (see map). At ...
, and was eventually cancelled in 2010.


Height distinction debate


"World's Tallest Tower" title

''
Guinness World Records ''Guinness World Records'', known from its inception in 1955 until 1999 as ''The Guinness Book of Records'' and in previous United States editions as ''The Guinness Book of World Records'', is a reference book published annually, listing world ...
'' has called the CN Tower "the world's tallest self-supporting tower" and "the world's tallest free-standing tower". Reference is on page 275. Although Guinness did list this description of the CN Tower under the heading "tallest building" at least once, it has also listed it under "tallest tower", omitting it from its list of "tallest buildings." In 1996, Guinness changed the tower's classification to "World's Tallest Building and Freestanding Structure".
Emporis Emporis GmbH was a real estate data mining company that was headquartered in Hamburg, Germany. The company collected data and photographs of buildings worldwide, which were published in an online database from 2000 to September 2022. On 12 Sept ...
and the Council on Tall Buildings and Urban Habitat both listed the CN Tower as the world's tallest free-standing structure on land, and specifically state that the CN Tower is not a true building, thereby awarding the title of world's tallest building to
Taipei 101 Taipei 101 (; stylized as TAIPEI 101), formerly known as the Taipei World Financial Center, is a supertall skyscraper in Taipei, Taiwan. This building was officially classified as the world's tallest from its opening in 2004 until the 2009 ...
, which is shorter than the CN Tower. The issue of what was tallest became moot when Burj Khalifa, then under construction, exceeded the height of the CN Tower in 2007 (see below). Although the CN Tower contains a restaurant, a gift shop and multiple observation levels, it does not have floors continuously from the ground, and therefore it is not considered a building by the Council on Tall Buildings and Urban Habitat (CTBUH) or Emporis. CTBUH defines a building as "a structure that is designed for residential, business, or manufacturing purposes. An essential characteristic of a building is that it has floors." The CN Tower and other similar structures—such as the Ostankino Tower in Moscow, Russia; the Oriental Pearl Tower in
Shanghai Shanghai (; , , Standard Chinese, Standard Mandarin pronunciation: ) is one of the four Direct-administered municipalities of China, direct-administered municipalities of the China, People's Republic of China (PRC). The city is located on the ...
, China; The Strat in
Las Vegas Las Vegas (; Spanish for "The Meadows"), often known simply as Vegas, is the 25th-most populous city in the United States, the most populous city in the state of Nevada, and the county seat of Clark County. The city anchors the Las Veg ...
, Nevada, United States; and the
Eiffel Tower The Eiffel Tower ( ; french: links=yes, tour Eiffel ) is a wrought-iron lattice tower on the Champ de Mars in Paris, France. It is named after the engineer Gustave Eiffel, whose company designed and built the tower. Locally nicknamed ...
in
Paris Paris () is the capital and most populous city of France, with an estimated population of 2,165,423 residents in 2019 in an area of more than 105 km² (41 sq mi), making it the 30th most densely populated city in the world in 2020. Si ...
, France—are categorized as "towers", which are free-standing structures that may have observation decks and a few other habitable levels, but do not have floors from the ground up. The CN Tower was the tallest tower by this definition until 2010 (see below). Taller than the CN Tower are numerous
radio masts and towers Radio masts and towers are typically tall structures designed to support antennas for telecommunications and broadcasting, including television. There are two main types: guyed and self-supporting structures. They are among the tallest human-made ...
, which are held in place by
guy-wire A guy-wire, guy-line, guy-rope, or stay, also called simply a guy, is a tensioned cable designed to add stability to a free-standing structure. They are used commonly for ship masts, radio masts, wind turbines, utility poles, and tents. A ...
s, the tallest being the KVLY-TV mast in
Blanchard, North Dakota Blanchard is a census-designated place in Blanchard Township, Traill County, North Dakota, United States. The population was 26 at the 2010 census. Blanchard is near the North Dakota- Minnesota border, near the junction of state highways ...
, in the United States at tall, leading to a distinction between these and "free-standing" structures. Additionally, the Petronius Platform stands above its base on the bottom of the
Gulf of Mexico The Gulf of Mexico ( es, Golfo de México) is an ocean basin and a marginal sea of the Atlantic Ocean, largely surrounded by the North American continent. It is bounded on the northeast, north and northwest by the Gulf Coast of the United ...
, but only the top of this oil and natural gas platform are above water, and the structure is thus partially supported by its
buoyancy Buoyancy (), or upthrust, is an upward force exerted by a fluid that opposes the weight of a partially or fully immersed object. In a column of fluid, pressure increases with depth as a result of the weight of the overlying fluid. Thus the ...
. Like the CN Tower, none of these taller structures are commonly considered buildings. On September 12, 2007,
Burj Khalifa The Burj Khalifa (; ar, برج خليفة, , Khalifa Tower), known as the Burj Dubai prior to its inauguration in 2010, is a skyscraper in Dubai, United Arab Emirates. It is known for being the world’s tallest building. With a total height ...
, which is a hotel, residential and commercial building in Dubai, United Arab Emirates, and was formerly known as Burj Dubai before opening, passed the CN Tower's 553.33-metre height. The CN Tower held the record of tallest freestanding structure on land for over 30 years. After Burj Khalifa had been formally recognized by the Guinness World Records as the world's tallest freestanding structure, Guinness re-certified CN Tower as the world's tallest freestanding tower. The tower definition used by Guinness was defined by the Council on Tall Buildings and Urban Habitat as 'a building in which less than 50% of the construction is usable floor space'. ''Guinness World Records'' editor-in-chief Craig Glenday announced that Burj Khalifa was not classified as a tower because it has too much usable floor space to be considered to be a tower. CN Tower still held world records for highest above ground wine cellar (in 360 Restaurant) at 351 metres, highest above ground restaurant at 346 metres (Horizons Restaurant), and tallest free-standing concrete tower during Guinness's recertification. The CN Tower was surpassed in 2009 by the Canton Tower in Guangzhou, China, which stands at tall, as the world's tallest tower; which in turn was surpassed by the Tokyo Skytree in 2011, which currently is the tallest tower at in height. The CN Tower, as of 2018, stands as the ninth-tallest free-standing structure on land, remains the tallest free-standing structure in the
Western Hemisphere The Western Hemisphere is the half of the planet Earth that lies west of the prime meridian (which crosses Greenwich, London, United Kingdom) and east of the antimeridian. The other half is called the Eastern Hemisphere. Politically, the te ...
, and is the third-tallest tower.


Height records

Since its construction, the tower has gained the following world height records:


Use

The CN Tower has been and continues to be used as a communications tower for a number of different media and by numerous companies.


Television broadcasters


Radio

There is no AM broadcasting on the CN Tower. The FM broadcasting, FM transmitters are situated in a metal broadcast antenna, on top of the main concrete portion of the tower at an elevation above .


Communications

* Bell Canada * Toronto Transit Commission * Amateur radio repeaters "2-Tango" (Very high frequency, VHF) and "4-Tango" (440/70 cm
UHF Ultra high frequency (UHF) is the ITU designation for radio frequencies in the range between 300 megahertz (MHz) and 3 gigahertz (GHz), also known as the decimetre band as the wavelengths range from one meter to one tenth of a meter (on ...
) — owned and operated by the Toronto FM Communications Society, under callsign VE3TWR


In popular culture

The CN Tower has been featured in numerous films, television shows, music recording covers, and video games. The tower also has its own official mascot, which resembles the tower itself. *''
Highpoint Highpoint can refer to: * Highpoint, Florida, an unincorporated community near Tampa Bay *Highpoint Shopping Centre in Melbourne, Australia *Highpoint (building), an apartment building in London, United Kingdom. *Highpoint I, a set of 1930s apartme ...
'' is a Canadian 1982 action film starring Richard Harris, Christopher Plummer and Beverly D'Angelo. It features a shot of stuntman Dar Robinson jumping off of the CN Tower in 1979. *''Views (album), Views'' is a 2016 studio album released on April 29, 2016 by Canadian rapper Drake (musician), Drake. The cover artwork features Drake sitting atop the CN Tower in Toronto. Drake appeared significantly larger than life-size on the cover, and the CN Tower's Twitter account later confirmed it to be Photograph manipulation, photo edited.


See also

* Architecture of Toronto * List of tallest buildings in Toronto * List of tallest structures in Canada * List of tallest freestanding structures * List of tallest towers * List of tallest buildings and structures * List of tallest structures


References


External links


CBC Archives – CN Tower opens to the public. (Multimedia)

Official CN Tower Website

Edgewalk

The Design, Engineering and Construction of the CN Tower – 1972 through to 1976

A visual construction history of the CN Tower – at 40th year anniversaries

How the CN Tower was Built
- Art Of Engineering (YouTube documentary) {{DEFAULTSORT:Cn Tower Towers completed in 1976 Buildings and structures in Toronto Towers with revolving restaurants Canadian National Railway facilities Communication towers in Canada Observation towers in Canada Towers in Ontario Modernist architecture in Canada Stairways Transmitter sites in Canada Tourist attractions in Toronto WZMH Architects buildings Railway Lands Articles containing video clips 1976 establishments in Ontario