It is west of Manwoltae. It functioned as an astronomical and meteorological observatory in the early period of the building of the Koryo royal palace. Various astronomical and meteorological observations were carried out systematically such as eclipses, comets, meteor, abnormal weather phenomena and sunspots.
Materials related to over 30 observations about the sunspot are displayed in the Koryo Museum. It is registered as the World Cultural Heritage site.
