Walls have different types of towers. [P 003 / Qiangtai] towers are as high as the wall. This type of tower projects from the wall and has battlements on its outer edge. Ditai or dilou are two-storied towers with arched rooms on the ground floor which were used as barracks, and battlements with rooms of brick and wooden pillars on the second floor. The upper floor also has facilities for beacon signaling. Zhantai is the third type of tower. Bows and arrows were stored in these along with other types of ammunition.
Watch towers - which have been described as standing like fences on the Great Wall - were the last and latest improvements to the wall's defences. The watch towers had three levels: a bottom layer for cannons, a middle layer for shooting arrows and a top layer for observation turrets and battlements.
