Chengshanzi Mountain City

　　Chengshanzi Mountain City is located southwest of Dunhua City in Yanbian Korean Autonomous Prefecture, Jilin Province, on an isolated high mountain along the southern bank of the Dashih River, a tributary of the upper Mudan River. The city is named after the ancient fortress built atop Mount Chengzi.

　　The mountaintop is surrounded by an earthen and stone-built city wall, approximately 4.5 kilometers in length, with remnants of a palace site in the central area. Numerous artifacts from the Dongxia Kingdom have been unearthed here. During the late Jin Dynasty, this mountain city served as the Nanjing (Southern Capital) of the Dongxia Kingdom.

　　The city walls form an irregular ellipse, with a circumference of about 2,000 meters. The walls follow the undulating terrain along the mountainside. Constructed with a mixture of earth and stones, the base of the walls is 5–7 meters wide, with some sections exceeding 10 meters. The remaining height of the walls ranges from 1.5 to 2.5 meters. The layout of the city is lower in the northeast and higher in the southwest, tilting slightly toward the northeast based on the terrain. The northern wall sits atop a steep cliff over 40 meters high, resulting in a relatively low wall. At the western end of the northern wall, the structure turns southeast, forming an acute angle at the corner. After a short stretch, there is a gate — the west gate — which is 4 meters wide. On the western side of the gate, the wall curves inward from the outside in a circular hook shape, resembling a fortress. Moving southeast from the west gate, the walls ascend gradually along a steep slope. Along this section, three “battlements” (马面) are positioned at varying distances due to the outward bulge of the mountain, serving for lookout and defense. The walls then descend sharply as they curve northeastward toward the higher part of the mountain. At the northeastern corner, the terrain flattens, and a gate — likely the east gate — is situated, slightly smaller than the west gate at 3 meters wide. The walls on both sides of the gate also curve inward from the outside, forming two fort-like structures. Outside the east gate, to the north, the terrain is relatively flat, about 100 meters from the riverbank, allowing access to water.

　　Inside the east gate and toward the southern side lies a large, gently sloping mountain hollow, where over 50 semi-subterranean house foundations remain. Most are rectangular, with larger ones measuring about 8 meters east-west and 6 meters north-south, and smaller ones around 6 meters east-west and 4 meters north-south. The centers of these house foundations are shallow pit-like depressions, with earthen walls about 20–40 centimeters high remaining on all sides. Each house has a door, mostly located in the middle of the eastern wall, though a few open to the north. A small number of house foundations can also be found on the southern slope of the mountain and the western part of the city.

　　Approximately 100 meters from the west gate, in the northwest part of the city, there is a stone-lined pool with a diameter of 4.6 meters, shaped like a pot bottom and 1 meter deep. Its bottom is paved with stones, and there is an outlet on the northern side that channels water through a small ditch down to the base of the cliff to the north. In the eastern part of the city, beneath a large expanse of house foundations, there is also a large reservoir.

　　In the central part of the city, there are several flattened, parade-ground-like areas, with the largest stretching over 100 meters. These were likely military drill grounds. Within and around the city, artifacts such as spearheads, iron swords, iron arrowheads, and Tang Dynasty coins like “Kaiyuan Tongbao” have been excavated.

　　Based on the relics and structure of Chengshanzi Mountain City, it is believed to be an early site of the Bohai Kingdom. In May 2006, Chengshanzi Mountain City was designated as part of the sixth group of Major Historical and Cultural Sites Protected at the National Level by the State Council.