This stunning hilltop fortress is a reminder of a time when Gongju (then called Ungjin) was Baekje’s capital. After entering through the grand stone Geumseoru West Gate, you can walk along the fortress' perimeter and on its wall. Along the way you'll pass numerous pavilions, including Gongbungnu and Gwangbongnu, rebuilt according to archaeological evidence of their original structures. The best views are in the northwest section overlooking the river. In the evening the fortress is lit by floodlights.
Notable structures inside the Gongsan-seong complex include Imnyu-gak, a banquet hall originally built in AD 500 (the building seen today is a replica); the Manharu Pavilion overlooking Gongju's central river Geum-gang, a building that once served twin purposes of defence and recreation; the pavilion Ssangsu-jeong, named for a pair of trees that King Injo used to lean against whilst contemplating the fate of his kingdom; and Yeongeun-sa, a temple first constructed in the 15th century that once served as a boarding house for warrior monks.
A changing of the guards ceremony takes place hourly between 11am and 5pm on weekends during April, May, September, October and November at the main entrance gate, where a stone arch stands opposite.