Pier and abutment introduction: The protruding part of the city wall is called a pier and abutment. The piers and abutments are also called "horse faces" and are part of the city wall construction. There are 12 piers and abutments on the city wall from Chongwen Gate to the turret, and one is built every 80 meters on the outer wall of the city wall. It is to enhance defense capabilities to eliminate enemies that enter the blind spots of the city wall. Among them, a pier located in the middle of the park is 39 meters long, which is the longest in the capital.