Introduction to the ruins of Huangdi City: Huangdi City is an irregular square rammed earth city, wide in the north and narrow in the south, with a difference of 30 meters. The north wall is 540 meters long and the south wall is 510 meters long. The east-west difference is 50 meters, the east wall is 500 meters long and the west wall is 450 meters long. The area is about 300 acres. The east, west and north walls of Huangdi City are relatively well preserved, while the south wall has several gaps and the southeast corner collapsed into the water of Xuanyuan Lake.