Representing the best of fortress construction of the late Baekje period(18 B.C-A.D. 660), this mountain fortress was linked to another one to the west, Geumseongsanseong, to form a defense line for the capital. Built along a ridge with earth and stone, it is about 5-6km long. The base of the wall is hardened clay, above which are layers of pressed rubble. As the inside part of the wall was made with dirt dug from the adjoining strip, a trench was formed along the wall within the fortress. The sites of a large military grain storage, a well called "Bride's Well" and a temple named Gyeongnyongsa are all that remain. The grain storage was in use as the Joseon period(1392-1910).