This astronomical observatory which is 2.8 meters high and a side of which is 2.6 meters long was built together with the royal palace in the beginning of Koryo Dynasty.
It was long used in astronomical observation, and did not operate since the collapse of Koryo Dynasty.
In the astronomy and geography section of “Koryosa”, a historic book, it was written that about 50 cases of sunspot was observed from 1105 up to the end of Koryo Dynasty, which shows that Koryo Dynasty began observing and studying the sunspot some hundreds of years earlier than Europe.
It was also recorded in 1281 that they created some observatory tools to measure the revolution of the sun and the moon and study their positions.
