Cheomseongdae Observatory

Overview

Cheomseongdae is the oldest surviving stone astronomical observatory in East Asia, built around 634 CE during the reign of Queen Seondeok of Silla. Standing 9.17 metres tall in an open field near Tumuli Park, the bottle-shaped tower is made from 362 granite blocks — one for each day of the lunar year.

Highlights

• Symbolic Architecture: The 12 base stones represent the 12 months; the 27 circular layers correspond to Queen Seondeok being the 27th ruler.
• Window Opening: A square window on the south face aligned so sunlight falls on the interior floor at the spring and autumn equinoxes.
• Night Lighting: The observatory is illuminated after dark, making it photogenic against the night sky.

History

Constructed under Queen Seondeok (r. 632–647 CE), Cheomseongdae was used by Silla astronomers to chart celestial movements for agriculture and the calendar. Its survival through 1,400 years of earthquakes and invasions is remarkable — a slight lean to the north is its only visible wear.

Visitor Tips

• Viewing only: You cannot enter or climb the observatory, but the surrounding field is open for photos.
• Free entry: No ticket required.
• Duration: 15–30 minutes; combine with Tumuli Park next door.