The ruins of Chang'an City in the Sui Daxing and Tang Dynasties are located in Xi'an City. It was the capital city site of the Sui and Tang dynasties. Daxing City was built on the model of Luoyang City left from the Han Dynasty, Jin Dynasty to Northern Wei Dynasty, so its specifications, outlines and unconsciously are very similar to Luoyang City, but it is more regular. In the Tang Dynasty, it was renamed Chang'an City, and the Daming Palace and Xingqing Palace were added. It was the most prosperous international metropolis in the world at that time. From the ruins, it can be seen that Daxing City is divided into three parts: Miyagi and Guocheng. Guocheng is mainly a residential area, the wall base is 9-12 meters wide and 6 meters high. Outside the city, there is a moat that is 9 meters wide and 4 meters deep. In addition, all the squares in Guocheng have square walls, which are 2.5-3 meters wide and 3 meters high. In Guocheng, there are 14 streets juxtaposed from north to south, 11 streets parallel to east and west, a total of 114 squares, neat and orderly. The ruins of Xuanwumen, Qinglong Temple, Mingdemen, Daming Palace, Xingqing Palace, etc. exist in the ruins of Chang'an City in Daxing and Tang Dynasty in Sui Dynasty.