Gyeongju was the capital of the Silla dynasty for 992 years. The Cheomseongdae Observatory is the oldest observatory in the world.

The strange structure of Cheomsongdae is an ancient astronomical observatory. It is probably the most well known of Korea's historic remains. The stone astronomical observatory was built during the reign of Queen Ssondeok in 634. The bottle-shaped tower was constructed on a square base. It is considered the oldest observatory in the world and one of the oldest man-made structures left in Korea. How it was operated is not known.