Cheomseongdae () is an astronomical observatory in Gyeongju, South Korea. Cheomseongdae is the oldest surviving astronomical observatory in Asia, and possibly even the world. It was constructed during the Silla 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.
Structure
Cheomseongdae stands 9.17 meters high and consists of three parts: a stylobate, or base upon which a column 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 character ().
The square stylobate base is 5.7 meters wide and built from a single layer of 12 rectangular stones. 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.
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 terms.
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.