Overlooking the lower stretch of the Geumgang River, this stone fortress measures 800m in circumference and the height of the wall ranges from three to four meters. Also known as Garimseong in historical records, the mountain fortress was built in 501 A.D. by a great Baekje (18 B.C.-A.D. 660) nobleman, Baek Ga, to protect the Baekje capital of Ungjin which is now Gongju. Upon its completion, Baek Ga became the fortress commander, rebelled against the Baekje king, Dongseong (479-501), and slew him. The rebellion did not last long, however, for as soon as he succeeded to the throne, King Muryeong (501-523) promptly quelled the rebellion and revenged his father by killing the rebel leader Baek Ga. Story has it that when Silla invaded Baekje to unify the Korean peninsula in 660 A.D., Seongheungsanseong was not attacked because of its rugged topography. The fort's garrison, however, on hearing of the fall of the Baekje capital, took their own lives.