Dongnamgangnu (Southeastern Pavilion) was built to defend Namsumun, the now destroyed floodgate. It was also used to defend Namgongsimdon, a strategic position where troops were stationed.
The stone structure the pavilion is built on is a gangu. A gangu is an elevated position that allows for surveillance of a large area of the fortress.
In times of peace, the Dongnamgangnu was used as a place of rest. During times of war, it was used as a command post by troops stationed in the area.
There are a total of four gangu present at Hwaseong Fortress.