The city wall, after its extensi on in the Ming Dynasty, stands 12 meters high. It is 12-14 meters wide across the top, 15-18 meters thick at the bottom and 13.7 kilometers in length. There is a rampart eery 120 meters apart, that extends out from the main wall. The top of the rampart is at the same level as the top of the wall. The ramparts were built to allow soldiers to see those enemies who would try to climb the wall. The distance between every two would try to climb the wall. The distance between every two ramparts is just within the range of arrow shot from either side. This allowed soldiers to protect the entire wall without exposing themselves to the enemy. There are altogether 98 of them on the wall ; each has a sentry building on top of it.
The weapons in ancient time were primitive. The gates of the city wall were the only way to go into and out of town. Therefore, these gates were important, strategic points. The feudal rulers racked their brains to try to defend them. In Xi'an, each of the east, west, south and north gates consists of three gate towers. The main is called zhenglou. Zhalou is the gate tower
with a suspension bridge, and Jianlou tower. Zhalou tower stands away from the wall. It is used to lift and lower the suspension bridge. Jianlou tower is in the center of the others. There are square windows in the front and on the two sides to shoot arrows from. The zhenglou to tower is the inner one and is also the main entrance to the city. Jianlou and zhenglou are connected by walls and the encircled area is called wongcheng in which could be stationed. From wongcheng, there are also horse passages leading to the top of the wall. There are gradually ascending steps that make it easy for war horses to ascend and descend. There are altogether eleven horse passages around the city .A watch tower is located on each of the four corners of the wall. The one at the southwestern corner is round, probably after the model of the imperial city wall of the Tang Dynasty, but the other three are square, higher and larger than the sentry building on the ramparts. This shows the strategic importance of the corners of the city wall in war time.
Along the outer crest of the city wall, there are crenellations or battlements, 5,984 of them. Under each crenel there is a square hole, from which arrows were shot and watch was kept. The lower inner wall on the top of the city wall is called parapets. They have no crenels. They were
designed to prevent soldiers from falling off the wall when traveling back and forth on its top. The city wall of Xi'an was first built of earth, rammed layer upon layer. The base layer was made of earth, quicklime, and glutinous rice extract, tempered together. It made the wall extremely strong and firm. Later, the wall was totally coated with bricks. On top of the wall, there is a brick water passage trough every 40-60 meters. They are used for drainage. They have played a very important role in the long-term protection of the city, once lifted.
Thus, the Ming Dynasty city wall formed a complex and well-organized system of defense. It is also the most complete city wall itself is a true display of the ability and wisdom of the working people in ancient time. It provides invaluable and substantial material for the study of the history, military science, and architecture of the Ming Dynasty.
