Hongjimun Gate and Tangchundae Fortress

Tangchundae Fortress is a unique defensive structure that demonstrates the capital defense system of the late Joseon Dynasty, built to connect Hanyang's city wall with Bukhansanseong Fortress. It served as a kind of gateway fortress (關門城) that linked the two walls to suit the terrain of the blind spot between the city wall and Bukhansanseong Fortress. The fortress wall is approximately 4 km in circumference, and within the fortress, a military training ground called Yeonyungdae (鍊戎臺) was built, along with military supply warehouses. The walls are neatly stacked with evenly sized square stones, showcasing the masonry techniques of King Sukjong's reign.

Hongjimun Gate features a gate tower with 3 front bays and 2 side bays on a stone arch, with a hip roof like most city gates. Next to it, the five-span water gate called Ogansudaemun was used as a water outlet with five arched openings.