A "Chi" is a bastion or turret-shaped projection strategically positioned at regular intervals along Hwaseong Fortress, enabling soldiers to defend the fort and repel approaching enemies. Hwaseong Fortress comprises 10 bastions, with slight variations in shape depending on the topography. Along the Eastern Wall, there exist three Chiseong known as Dongilchi, Dongyichi, and Dongsamchi. Ordinarily, numbering started from the north, making the southernmost bastion Dongsamchi, literally meaning the eastern third bastion.

Dongsamchi is located between Dongiporu or Eastern Guard Post II and Dongnamgangnu or Southeastern Corner Pavilion. Due to the steep slope in the area, Dongsamchi possesses the widest width and the shortest length among the bastions. Initially erected by King Jungjo in 1796 during the Joseon Dynasty, it underwent restoration in 1979, preserving the bastion and its surrounding fortress in their original appearance.