A tower is a tall

structure A structure is an arrangement and organization of interrelated elements in a material object or system, or the object or system so organized. Material structures include man-made objects such as buildings and machines and natural objects such as ...

, taller than it is wide, often by a significant factor. Towers are distinguished from masts by their lack of

guy-wires A guy-wire, guy-line, guy-rope, down guy, or stay, also called simply a guy, is a tensioned cable designed to add stability to a freestanding structure. They are used commonly for ship masts, radio masts, wind turbines, utility poles, and ten ...

and are therefore, along with tall buildings, self-supporting structures. Towers are specifically distinguished from

building A building or edifice is an enclosed Structure#Load-bearing, structure with a roof, walls and window, windows, usually standing permanently in one place, such as a house or factory. Buildings come in a variety of sizes, shapes, and functions, a ...

s in that they are built not to be habitable but to serve other functions using the

height Height is measure of vertical distance, either vertical extent (how "tall" something or someone is) or vertical position (how "high" a point is). For an example of vertical extent, "This basketball player is 7 foot 1 inches in height." For an e ...

of the tower. For example, the height of a

clock tower Clock towers are a specific type of structure that house a turret clock and have one or more clock faces on the upper exterior walls. Many clock towers are freestanding structures but they can also adjoin or be located on top of another building ...

improves the visibility of the clock, and the height of a tower in a fortified building such as a

castle A castle is a type of fortification, fortified structure built during the Middle Ages predominantly by the nobility or royalty and by Military order (monastic society), military orders. Scholars usually consider a ''castle'' to be the private ...

increases the visibility of the surroundings for defensive purposes. Towers may also be built for

observation Observation in the natural sciences is an act or instance of noticing or perceiving and the acquisition of information from a primary source. In living beings, observation employs the senses. In science, observation can also involve the percep ...

, leisure, or

telecommunication Telecommunication, often used in its plural form or abbreviated as telecom, is the transmission of information over a distance using electronic means, typically through cables, radio waves, or other communication technologies. These means of ...

purposes. A tower can stand alone or be supported by adjacent buildings, or it may be a feature on top of a larger structure or building.

Etymology

Old English Old English ( or , or ), or Anglo-Saxon, is the earliest recorded form of the English language, spoken in England and southern and eastern Scotland in the Early Middle Ages. It developed from the languages brought to Great Britain by Anglo-S ...

''torr'' is from

Latin Latin ( or ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally spoken by the Latins (Italic tribe), Latins in Latium (now known as Lazio), the lower Tiber area aroun ...

''turris'' via

Old French Old French (, , ; ) was the language spoken in most of the northern half of France approximately between the late 8th

Greek Greek may refer to: Anything of, from, or related to Greece, a country in Southern Europe: *Greeks, an ethnic group *Greek language, a branch of the Indo-European language family **Proto-Greek language, the assumed last common ancestor of all kno ...

τύρσις was loaned from a pre-Indo-European Mediterranean language, connected with the Illyrian toponym Βου-δοργίς. With the Lydian language">Lydian toponyms Τύρρα, Τύρσα, it has been connected with the ethnonym Tyrrhenians">Τυρρήνιοι as well as with ''Tusci'' (from ''*Turs-ci''), the Greek and Latin names for the Etruscans (Kretschmer Glotta 22, 110ff.)

History

Towers have been used by humankind since prehistoric times. The oldest known may be the circular stone tower in walls of Wall of Jericho (Neolithic), Neolithic Jericho (8000 BC). Some of the earliest towers were

ziggurat A ziggurat (; Cuneiform: 𒅆𒂍𒉪, Akkadian: ', D-stem of ' 'to protrude, to build high', cognate with other Semitic languages like Hebrew ''zaqar'' (זָקַר) 'protrude'), ( Persian: Chogha Zanbilچغازنجبیل) is a type of massive ...

s, which existed in

Sumerian architecture The architecture of Mesopotamia is ancient architecture of the region of the Tigris–Euphrates river system (also known as Mesopotamia), encompassing several distinct cultures and spanning a period from the 10th millennium BC (when the first pe ...

since the 4th millennium BC. The most famous ziggurats include the Sumerian

Ziggurat of Ur The Ziggurat (or Great Ziggurat) of Ur ( Sumerian: "Etemenniguru", meaning "house whose foundation creates terror") is a Neo-Sumerian ziggurat in what was the city of Ur near Nasiriyah, in present-day Dhi Qar Province, Iraq. The structure ...

, built in the 3rd millennium BC, and the

Etemenanki Etemenanki () was a ziggurat dedicated to the Mesopotamian god Marduk in the ancient city of Babylon. It now exists only in ruins, located about south of Baghdad, Baghdad, Iraq. Many scholars have identified Etemenanki as the ziggurat for the bi ...

, one of the most famous examples of Babylonian architecture. Some of the earliest surviving examples are the

broch In archaeology, a broch is an British Iron Age, Iron Age drystone hollow-walled structure found in Scotland. Brochs belong to the classification "complex Atlantic roundhouse" devised by Scottish archaeologists in the 1980s. Brochs are round ...

structures in northern

Scotland Scotland is a Countries of the United Kingdom, country that is part of the United Kingdom. It contains nearly one-third of the United Kingdom's land area, consisting of the northern part of the island of Great Britain and more than 790 adjac ...

, which are conical

tower house A tower house is a particular type of stone structure, built for defensive purposes as well as habitation. Tower houses began to appear in the Middle Ages, especially in mountainous or limited access areas, to command and defend strategic points ...

s. These and other examples from

Phoenicia Phoenicians were an Ancient Semitic-speaking peoples, ancient Semitic group of people who lived in the Phoenician city-states along a coastal strip in the Levant region of the eastern Mediterranean, primarily modern Lebanon and the Syria, Syrian ...

n and

Roman Roman or Romans most often refers to: *Rome, the capital city of Italy *Ancient Rome, Roman civilization from 8th century BC to 5th century AD *Roman people, the people of Roman civilization *Epistle to the Romans, shortened to Romans, a letter w ...

cultures emphasised the use of a tower in fortification and sentinel roles. For example, the name of the Moroccan city of

Mogador Essaouira ( ; ), known until the 1960s as Mogador (, or ), is a port city in the western Morocco, Moroccan region of Marrakesh-Safi, on the Atlantic Ocean, Atlantic coast. It has 77,966 inhabitants as of 2014. The foundation of the city of Essao ...

, founded in the first millennium BC, is derived from the Phoenician word for

watchtower A watchtower or guardtower (also spelt watch tower, guard tower) is a type of military/paramilitary or policiary tower used for guarding an area. Sometimes fortified, and armed with heavy weaponry, especially historically, the structures are ...

('migdol'). The Romans utilised octagonal towers as elements of

Diocletian's Palace Diocletian's Palace (, ; ) is an ancient Roman palace and fortress complex built at the end of the third century AD by the Roman Emperor Diocletian as his retirement residence. About half of the complex was for Diocletian's personal use, with th ...

Croatia Croatia, officially the Republic of Croatia, is a country in Central Europe, Central and Southeast Europe, on the coast of the Adriatic Sea. It borders Slovenia to the northwest, Hungary to the northeast, Serbia to the east, Bosnia and Herze ...

, which monument dates to approximately 300 AD, while the

Servian Walls The Servian Wall (; ) is an ancient Roman defensive barrier constructed around the city of Rome in the early 4th century BC. The wall was built of volcanic tuff and was up to in height in places, wide at its base, long, and is believed to hav ...

(4th century BC) and the

Aurelian Walls The Aurelian Walls () are a line of city walls built between 271 AD and 275 AD in Rome, Italy, during the reign of the Roman Emperor Aurelian. They superseded the earlier Servian Wall built during the 4th century BC. The walls enclosed all the ...

(3rd century AD) featured square ones. The Chinese used towers as integrated elements of the

Great Wall of China The Great Wall of China (, literally "ten thousand ''li'' long wall") is a series of fortifications in China. They were built across the historical northern borders of ancient Chinese states and Imperial China as protection against vario ...

in 210 BC during the

Qin dynasty The Qin dynasty ( ) was the first Dynasties of China, imperial dynasty of China. It is named for its progenitor state of Qin, a fief of the confederal Zhou dynasty (256 BC). Beginning in 230 BC, the Qin under King Ying Zheng enga ...

. Towers were also an important element of

castles A castle is a type of fortified structure built during the Middle Ages predominantly by the nobility or royalty and by military orders. Scholars usually consider a ''castle'' to be the private fortified residence of a lord or noble. This i ...

. Other well known towers include the

Leaning Tower of Pisa The Leaning Tower of Pisa ( ), or simply the Tower of Pisa (), is the , or freestanding bell tower, of Pisa Cathedral. It is known for its nearly four-degree lean, the result of an unstable Foundation (engineering), foundation. The tower is on ...

Pisa, Italy Pisa ( ; ) is a city and ''comune'' (municipality) in Tuscany, Central Italy, straddling the Arno just before it empties into the Ligurian Sea. It is the capital city of the Province of Pisa. Although Pisa is known worldwide for the Leaning Tow ...

built from 1173 until 1372, the Two Towers in

Bologna, Italy Bologna ( , , ; ; ) is the capital and largest city of the Emilia-Romagna region in northern Italy. It is the List of cities in Italy, seventh most populous city in Italy, with about 400,000 inhabitants and 150 different nationalities. Its M ...

built from 1109 until 1119 and the Towers of Pavia (25 survive), built between 11th and 13th century. The Himalayan Towers are stone towers located chiefly in

Tibet Tibet (; ''Böd''; ), or Greater Tibet, is a region in the western part of East Asia, covering much of the Tibetan Plateau and spanning about . It is the homeland of the Tibetan people. Also resident on the plateau are other ethnic groups s ...

built approximately 14th to 15th century. Dana Thomas, "Towers to the Heavens"
''Newsweek'', 2003-11-15

Mechanics

Up to a certain height, a tower can be made with the supporting structure with parallel sides. However, above a certain height, the compressive load of the material is exceeded, and the tower will fail. This can be avoided if the tower's support structure tapers up the building. A second limit is that of buckling—the structure requires sufficient stiffness to avoid breaking under the loads it faces, especially those due to winds. Many very tall towers have their support structures at the periphery of the building, which greatly increases the overall stiffness. A third limit is dynamic; a tower is subject to varying winds, vortex shedding, seismic disturbances etc. These are often dealt with through a combination of simple strength and stiffness, as well as in some cases

tuned mass damper A tuned mass damper (TMD), also known as a harmonic absorber or seismic damper, is a device mounted in structures to reduce mechanical vibrations, consisting of a mass mounted on one or more damped springs. Its oscillation frequency is tune ...

s to damp out movements. Varying or tapering the outer aspect of the tower with height avoids vibrations due to vortex shedding occurring along the entire building simultaneously.

Functions

Although not correctly defined as towers, many modern

high-rise building A tower block, high-rise, apartment tower, residential tower, apartment block, block of flats, or office tower is a tall building, as opposed to a low-rise building and is defined differently in terms of height depending on the jurisdiction ...

s (in particular

skyscraper A skyscraper is a tall continuously habitable building having multiple floors. Most modern sources define skyscrapers as being at least or in height, though there is no universally accepted definition, other than being very tall high-rise bui ...

) have 'tower' in their name or are colloquially called 'towers'. Skyscrapers are more properly classified as 'buildings'. In the

United Kingdom The United Kingdom of Great Britain and Northern Ireland, commonly known as the United Kingdom (UK) or Britain, is a country in Northwestern Europe, off the coast of European mainland, the continental mainland. It comprises England, Scotlan ...

, tall domestic buildings are referred to as tower blocks. In the

United States The United States of America (USA), also known as the United States (U.S.) or America, is a country primarily located in North America. It is a federal republic of 50 U.S. state, states and a federal capital district, Washington, D.C. The 48 ...

, the original World Trade Center had the nickname the Twin Towers, a name shared with the

Petronas Twin Towers The Petronas Towers (), also known as the Petronas Twin Towers and colloquially the KLCC Twin Towers, are an interlinked pair of 88-storey supertall skyscrapers in Kuala Lumpur, Malaysia, standing at . From 1996 to 2004, they were the tall ...

Kuala Lumpur Kuala Lumpur (KL), officially the Federal Territory of Kuala Lumpur, is the capital city and a Federal Territories of Malaysia, federal territory of Malaysia. It is the largest city in the country, covering an area of with a census population ...

. In addition some of the structures listed below do not follow the strict criteria used at

List of tallest towers The tallest structure in the world is the Burj Khalifa skyscraper at . Listed are guyed masts (such as telecommunication masts), self-supporting towers (such as the CN Tower), skyscrapers (such as the Willis Tower), oil platforms, electricity ...

Strategic advantages

The tower throughout history has provided its users with an advantage in surveying defensive positions and obtaining a better view of the surrounding areas, including battlefields. They were constructed on

defensive walls A defensive wall is a fortification usually used to protect a city, town or other settlement from potential aggressors. The walls can range from simple palisades or earthworks to extensive military fortifications such as curtain walls with to ...

, or rolled near a target (see

siege tower A Roman siege tower or breaching tower (or in the Middle Ages, a belfry''Castle: Stephen Biesty's Cross-Sections''. Dorling Kindersley Pub (T); 1st American edition (September 1994). Siege towers were invented in 300 BC. ) is a specialized siege ...

). Today, strategic-use towers are still used at prisons, military camps, and defensive perimeters.

Potential energy

By using gravity to move objects or substances downward, a tower can be used to store items or liquids like a

storage silo A silo () is a structure for storing Bulk material handling, bulk materials. Silos are commonly used for bulk storage of grain, coal, cement, carbon black, woodchips, food products and sawdust. Three types of silos are in widespread use toda ...

or a

water tower A water tower is an elevated structure supporting a water tank constructed at a height sufficient to pressurize a water distribution system, distribution system for potable water, and to provide emergency storage for fire protection. Water towe ...

, or aim an object into the earth such as a drilling tower. Ski-jump ramps use the same idea, and in the absence of a natural mountain slope or hill, can be human-made.

Communication enhancement

In history, simple towers like

lighthouse A lighthouse is a tower, building, or other type of physical structure designed to emit light from a system of lamps and lens (optics), lenses and to serve as a beacon for navigational aid for maritime pilots at sea or on inland waterways. Ligh ...

bell tower A bell tower is a tower that contains one or more bells, or that is designed to hold bells even if it has none. Such a tower commonly serves as part of a Christian church, and will contain church bells, but there are also many secular bell to ...

s, signal towers and

minaret A minaret is a type of tower typically built into or adjacent to mosques. Minarets are generally used to project the Muslim call to prayer (''adhan'') from a muezzin, but they also served as landmarks and symbols of Islam's presence. They can h ...

s were used to communicate information over greater distances. In more recent years,

radio mast Radio masts and towers are typically tall structures designed to support antenna (radio), antennas for telecommunications and broadcasting, including television. There are two main types: guyed and self-supporting structures. They are among the ...

s and cell phone towers facilitate communication by expanding the range of the transmitter. The

CN Tower The CN Tower () is a communications and observation tower in Toronto, Ontario, Canada. Completed in 1976, it is located in downtown Toronto, built on the former Railway Lands. Its name "CN" referred to Canadian National, the railway co ...

Toronto, Ontario Toronto ( , locally pronounced or ) is the List of the largest municipalities in Canada by population, most populous city in Canada. It is the capital city of the Provinces and territories of Canada, Canadian province of Ontario. With a p ...

, Canada was built as a communications tower, with the capability to act as both a transmitter and repeater.

Transportation support

Towers can also be used to support bridges, and can reach heights that rival some of the tallest buildings above-water. Their use is most prevalent in

suspension bridge A suspension bridge is a type of bridge in which the deck (bridge), deck is hung below suspension wire rope, cables on vertical suspenders. The first modern examples of this type of bridge were built in the early 1800s. Simple suspension bridg ...

s and

cable-stayed bridge A cable-stayed bridge has one or more ''towers'' (or ''pylons''), from which wire rope, cables support the bridge deck. A distinctive feature are the cables or wikt:stay#Etymology 3, stays, which run directly from the tower to the deck, norm ...

s. The use of the pylon, a simple tower structure, has also helped to build railroad bridges, mass-transit systems, and harbors.

Control tower Air traffic control (ATC) is a service provided by ground-based air traffic controllers who direct aircraft on the ground and through a given section of controlled airspace, and can provide advisory services to aircraft in non-controlled a ...

s are used to give visibility to help direct aviation traffic.

Other

* To access tall or high objects: launch tower, service tower, service structure, scaffold,

tower crane A crane is a machine used to move materials both vertically and horizontally, utilizing a system of a boom, hoist, wire ropes or chains, and sheaves for lifting and relocating heavy objects within the swing of its boom. The device uses on ...

* To access atmospheric conditions aloft:

wind turbine A wind turbine is a device that wind power, converts the kinetic energy of wind into electrical energy. , hundreds of thousands of list of most powerful wind turbines, large turbines, in installations known as wind farms, were generating over ...

, meteorological measurement tower, tower telescope,

solar power Solar power, also known as solar electricity, is the conversion of energy from sunlight into electricity, either directly using photovoltaics (PV) or indirectly using concentrated solar power. Solar panels use the photovoltaic effect to c ...

station * To lift high tension cables for electrical power distribution

transmission tower A transmission tower (also electricity pylon, hydro tower, or pylon) is a tall structure, usually a lattice tower made of steel that is used to support an overhead power line. In electrical grids, transmission towers carry high-voltage transmis ...

* To take advantage of the temperature gradient inherent in a height differential:

cooling tower A cooling tower is a device that rejects waste heat to the atmosphere through the cooling of a coolant stream, usually a water stream, to a lower temperature. Cooling towers may either use the evaporation of water to remove heat and cool the ...

* To expel and disperse potentially harmful gases and particulates into the atmosphere:

chimney A chimney is an architectural ventilation structure made of masonry, clay or metal that isolates hot toxic exhaust gases or smoke produced by a boiler, stove, furnace, incinerator, or fireplace from human living areas. Chimneys are typical ...

* To protect from exposure: BREN Tower, lightning rod tower * For industrial production: shot tower * For surveying: Survey tower * To drop objects: Drop tube (drop tower), bomb tower, diving platform * To test height-intensive applications:

elevator test tower An elevator test tower is a structure usually 100 to over 200 metres (300 feet to over 600 feet) tall that is designed to evaluate the stress and fatigue limits of specific elevator cars in a controlled environment. Tests are also carried out in t ...

* To improve structural integrity: thyristor tower * To mimic towers or provide height for training purposes:

fire tower A fire lookout tower, fire tower, or lookout tower is a tower that provides housing and protection for a person known as a " fire lookout", whose duty it is to search for wildfires in the wilderness. It is a small building, usually on the summit ...

, parachute tower * As art: Shukhov Tower * For recreation: rock climbing tower * As a symbol:

Tower of Babel The Tower of Babel is an origin myth and parable in the Book of Genesis (chapter 11) meant to explain the existence of different languages and cultures. According to the story, a united human race speaking a single language migrates to Shin ...

, The Tower (Tarot card),

church tower Church may refer to: Religion * Church (building), a place/building for Christian religious activities and praying * Church (congregation), a local congregation of a Christian denomination * Church service, a formalized period of Christian comm ...

The term "tower" is also sometimes used to refer to firefighting equipment with an extremely tall ladder designed for use in firefighting/rescue operations involving high-rise buildings.

Gallery

References

External links

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