Geumiseong is a mountain fortress built on the summit of Geumseongsan Mountain, which rises 430 meters above sea level. It overlooks Jeonui and Cheonan to the north and Geumgang River to the south. The architecture style of Geumiseong Fortress is a combination of the styles of the Baekje dynasty and the early Unified Silla. Based on the relics found inside the fortress, it is thought to have been built in the Goryeo period. The robustness of the fortress takes advantage of the rugged topography, so much so that it had been known as ironclad bastion among common people.

The eastern side of the fortress has considerably collapsed, but the southern part is in a relatively good condition. The western and northern walls are also in bad conditions.

Some earthenware pieces were found where there once stood a watchtower. Also, some pieces of roof tiles were found where there was a fortress building in the central part of the fortress on mountain summit. The earthenware pieces are hard porcelain and soft glass wares like bowls and pots. The tile pieces mostly feature fishbone patterns in dark gray color.