At the time of this picture, Beijing was divided into two separate sections each enclosed by its own walls which measured about thirty feet (9 m) in height for a thickness of about twenty feet (6 m). The bases were made of stone, the upper parts of brick and the summit was floored with tiles. It is said that twelve horsemen could ride abreast on the tiled floor.
In front of each main gate was an esplanade, used as a place of arms where access was not located directly in front of the inner gate, but laterally. Above and behind the gates, watchtowers rose nine stories.