Cheomseongdae is a stone building of the mid-Silla period located in the northeastern part of Banwolseong Fortress in Gyeongju.

The astronomical observatory of the Silla Dynasty, which used to observe the movements of celestial bodies, is about nine meters high.

It is known as the oldest observatory in the East, which was built during the reign of Queen Seondeok, and is a valuable cultural asset that shows the high level of science of the time.

It was designated as National Treasure No. 31 on December 20, 1962.