The Acha Mountain Fortress (Historic Site No. 234), which spreads over Gwangjang-dong covering 133,700, is also called as Janghan Castle or Gwangjang castle. During the three-nation Era, Baekje selected Gwangju, Kyunggi-do as the capital and built the fortress to prepare for the attack by their enemy, Goguryeo.

One kilometer wide and ten meters high, it is famous as being the death place of the Goguryeo`s General, Ondal, in a battle against the Shilla, to recover the lost territory north of Jukyeong. Now there are only ruins of the fortress that remain.

With Yongma Mountain, it has turned into an airy place that keeps residents healthy and gives them new energy. There are hiking trails, drinking fountains of mineral water, badminton courts as well as archery lanes, Palgakjeong (the octagon pavilion with a beautiful view) and playgrounds. The Acha Mountain Fortress will soon be restored to become the location of the `youth history plaza`.