It is a stone staircase at the royal palace site of Gongsanseong Fortress. Gongju Gongsanseong Fortress is a fortress from the Baekje period located in Sanseong-dong, Gongju-si, Chungcheongnam-do, Historic Site No. 12 of the Cultural Heritage Designation Number. At the time of Baekje, it was called Woongjinseong Fortress, but after the Goryeo Dynasty, it was called Gongsanseong Fortress. Gongsanseong Fortress was referred to as the center of local administration not only during the Baekje period but also during the Joseon Dynasty.