Gongsanseong

Gongsanseong () is a castle in Gongju, South Chungcheong Province, South Korea.

==Description== Gongsanseong was initially known as Ungjinseong and subsequently as Gongsanseong during the reign of the Goryeo Dynasty. It occupies an area of , presently in the Geumseong-dong and Sanseong-dong districts. It was unearthed during the archaeological excavations done after 1980s, when the constriction methods in building the forts's rampart, the royal palace, and the associated structures of the royal palace were revealed. The fort is located atop the Gongsan mountain (elevation ) and extends over a length of , with its stone wall in length and the balance made of earth. It was built as a defense fortification adapted to the local topography by linking mountain peaks and bridging the valleys. Following the collapse of the Baekje empire, the ramparts were rebuilt fully as stone walls. The fortress has been illuminated. It functioned both as a defense structure and a royal palace.