Cheomseongdae () is an astronomical observatory in

Gyeongju Gyeongju (, ), historically known as Seorabeol (, ), is a coastal city in the far southeastern corner of North Gyeongsang Province, South Korea. It is the second largest city by area in the province after Andong, covering with a population of ...

, South Korea. Cheomseongdae is the oldest surviving astronomical observatory in Asia, and possibly even the world. It was constructed during the

Silla Silla (; Old Korean: wikt:徐羅伐#Old Korean, 徐羅伐, Yale romanization of Korean, Yale: Syerapel, Revised Romanization of Korean, RR: ''Seorabeol''; International Phonetic Alphabet, IPA: ) was a Korean kingdom that existed between ...

period, during the reign of Queen Seondeok (r. 632–647 AD). Cheomseongdae was designated as the country's 31st national treasure on December 20, 1962. It is part of Gyeongju Historic Areas, a UNESCO

World Heritage Site World Heritage Sites are landmarks and areas with legal protection under an treaty, international treaty administered by UNESCO for having cultural, historical, or scientific significance. The sites are judged to contain "cultural and natural ...

Structure

Cheomseongdae stands 9.17 meters high and consists of three parts: a stylobate, or base upon which a

column A column or pillar in architecture and structural engineering is a structural element that transmits, through compression, the weight of the structure above to other structural elements below. In other words, a column is a compression member ...

is constructed, a curved cylindrical body, and a square top. Midway up the body stands a square window and entrance to the inside of the structure. When viewed from above, Cheomseongdae resembles the Korean

Hanja Hanja (; ), alternatively spelled Hancha, are Chinese characters used to write the Korean language. After characters were introduced to Korea to write Literary Chinese, they were adapted to write Korean as early as the Gojoseon period. () ...

character (Hangul: ), meaning "well." The square stylobate base is 5.7 meters wide and built from a single layer of 12 rectangular stones. From the base to the window, the tower is filled with earth and rubble. The cylindrical body of the tower is built out of 365 pieces of cut

granite Granite ( ) is a coarse-grained (phanerite, phaneritic) intrusive rock, intrusive igneous rock composed mostly of quartz, alkali feldspar, and plagioclase. It forms from magma with a high content of silica and alkali metal oxides that slowly coo ...

, symbolizing the number of days in a

year A year is a unit of time based on how long it takes the Earth to orbit the Sun. In scientific use, the tropical year (approximately 365 Synodic day, solar days, 5 hours, 48 minutes, 45 seconds) and the sidereal year (about 20 minutes longer) ...

. However, various historical documents have reported different numbers of stones. Song (1983) cites a 1962 survey of the site by Gyeongju National Museum director Hong Sa-jun, who found 366 blocks. This discrepancy in stone count may be attributed to some researchers including or omitting a stone slab inside the top of the tower and not visible from the outside. The stones are fashioned as annular sectors, meaning each stone takes the shape of a curved or bent rectangle. At the top, there are two tiers of (), and it is presumed that an observation device was placed on it. Its construction style parallels that used at the Bunhwangsa in Gyeongju.

Symbolism

The number and placement of the stones in Cheomseongdae have been theorized to represent various historical and astronomical figures. The central hole or window separates the body into 12 layers of stones both above and below, symbolizing the 12 months in a year and the 24

solar term A solar term (or ''jiéqì'', zh, t=節氣, s=节气) is any of twenty-four periods in traditional Chinese lunisolar calendars that matches a particular astronomical event or signifies some natural phenomenon. The points are spaced 15° apart ...

s. Additionally, the 12 stones which comprise the stylobate may also reference the 12 months. CheomseongdaeModel2

Preservation

Cheomseongdae's original appearance and shape has remained unchanged for over 1300 years; however the structure now tilts slightly to the north-east. In 2007, a system was installed to measure the state of Cheomseongdae every hour. Of particular concern are cracks and structural displacements, and movements of the foundation stones. Cheomseongdae is additionally susceptible to wear due to aging and weathering, particularly from air pollution and structural imbalance caused by ground subsidence. The exterior of the structure is regularly washed down to remove moss. The National Research Institute of Cultural Heritage in Korea has conducted inspections on the structure regularly since 1981. The Gyeongju municipal government oversees the site's management and preservation.

Popular culture

Cheomseongdae is mentioned in the popular

Korean drama Korean drama (), also known as K-drama or Koreanovela, refers to Korean language, Korean-language television shows made in South Korea. These shows began to be produced around the early 1960s, but were mostly consumed domestically until the rise ...

'' Queen Seondeok''. In the 2009 drama, Cheomseongdae was constructed when Queen Seondeok was still a princess; this was her first decree as a princess. Cheomseongdae was meant to share the knowledge of astronomy with everyone, rather than letting one person (Lady Misil) abuse the knowledge of it. By doing so, she also abdicated her divine rights. Because this was uncommon at the time and unsupported by many conservatives, at the opening of Cheomseongdae, barely any nobles showed up.

References

External links