It is the remains of a post station built in the Ming Dynasty (1368-1644). The Yicheng covers an area of 22,000 square meters with a square plane and a wall circumference of 1891.8 meters. The surface of the city wall is made of bricks and the inner layer is rammed earth. The wall is 8-11 meters wide at the bottom, 3-5 meters wide at the top and 11 meters high. Four corners are evenly distributed around the wall. East and west each opened a city gate and built a city building. There are smoke piers outside the city. Five roads crisscross the city, dividing the city into twelve regions of different sizes.