Dongnaeeupseong Fortress Site, Medieval fortress site in Dongnae District, South Korea

Dongnaeeupseong Fortress is a medieval military installation in Dongnae District featuring a wall that extends roughly 2.7 kilometers (1.7 mi) with six gates. Each gate is topped by a traditional Korean gatehouse and accompanied by defensive structures that form the complete fortification system.

The first written record of Dongnaeeupseong is a repair of the Dongnae fortress wall in 1021, during King Hyeonjong's reign in Goryeo. In 1387, under King U, it was enlarged against Japanese raiders to a circuit of 3,090 ja and a height of 13 ja. After the 1592 Siege of Dongnae, where prefect Song Sang-hyeon and his garrison died, the fortress lay neglected until prefect Jeong Eon-seop rebuilt it in 1731 with a circuit of 1,729 ja and four gates.

The fortress displays how Koreans built military defenses through its oval design and multiple gates positioned across the hillside. These structures show the practical thinking behind traditional Korean fortification methods.

The walls run from the hill behind Chungnyeolsa Shrine over Maansan to the ridge behind Dongnae Hyanggyo, with the north and east sides on high ground and the south and west opening onto the flat town centre. Much of the flatland wall was removed during the Japanese colonial period, so the surviving and restored sections are mainly on the hillside. Lights are switched on at night along the walking trail.

Excavations since 1979 have uncovered artifacts and human remains from the 16th-century Japanese invasions buried beneath the ruins. These discoveries reveal stories of those who defended the fortress during that turbulent period.