Chungcheong Suyeongseong Fortress is a stone wall to defend against foreign enemies from the West Sea.

It was built by Lee Jang-saeng, the Naval Commander-in-chief, during the 4th year of King Jungjong of the Joseon Dynasty (1509) reign. The fortress, a wall of stacked stones extending for 1,650 meters on the perimeter of Chungcheong Naval Base, was a strategically important point for coastal defense. An observatory was built on a high land shaped like a soft-shelled turtle to watch over the seas and islands.

There were four fortress gates on all sides, a small western gate, and government offices, such as Yeongbojeong, Gwandeokjeong, Daeseopru, Neungheogak, and Gosodae, all of which were destroyed. Manghwamun (western gate) and Jinhyulcheong, Janggyocheong, and Gonghaegwan (buildings) have been preserved.

Manghwamun Gate is shaped like an arch built with cleaning granites. Ocheonhang Port was called Hoeipo, where trade was carried out with China since the Baekje Dynasty, and it hosted military vessels to repel Japanese pirates during the Goryeo Dynasty. In the 12th year of King Sejo's reign (1466), the naval base was constructed as the headquarters of the Chungcheong Provincial Navy to defend the western coast.