Platform base introduction: The first floor of Zhenbei Platform is the base, which is 82 meters long in the north, 76 meters long in the south, 64 meters long in the east and west, 320 meters in circumference and 12 meters in depth. It is surrounded by walls, the inner wall is 5.5 meters high, the outer wall is 10 meters high, with crenellations on it, a city gate on the south side of the east wall, and a masonry horse road on the southeast side.