Gongshimdon is a watchtower built in the northeast of Hwaseong Fortress to surveil and defend against surrounding threats. Gongshimdon was originally built by King Jungjo in 1796 during the Joseon Dynasty. However, it was heavily destroyed during the Korean War (1950-1953) and was rebuilt in 1976.

The name of Gongshimdon means hollow outpost. The three-story cylindrical tower is built with circularly laid bricks and has no other facilities except a spiral staircase inside. In Korea, Namhansanseong Fortress and Ganghwa Island's coastal areas are similar in shape, but only Hwaseong Gongsimdon is constructed with hollow inside. In addition, the winding path up the stairway is shaped like a conch, called Sora in Korean, so the place was also called Soragak, literally meaning conch tower.