Hidden gate

Ammun (literally “dark gate”) refers to an auxiliary gate that was built at a point on a fortress wall where it could avoid enemy observation and be used to secretly transport supplies and reinforcements and to launch surprise attacks against an enemy outside the wall. There are currently sixteen auxiliary gates along the walls of Namhansanseong, including eleven along the main wall, four along the Bongamseong Extended Defensive wall, and one on the Hanbong Extended Defensive Wall.