It was built during the reign of Queen Seondeok ( 632 -- 647 ) .
Cheomseongdae near Gyeongju is the oldest extant astronomical observatory in East Asia but some disagree on its exact functions .
Gyeongju was built during the reign of Queen Seondeok ( 632 -- 647 ) .
Cheomseongdae near Gyeongju is the oldest extant astronomical observatory in East Asia but some disagree on its exact functions .