Chang 'an in Han Dynasty was very small, not as big as that in Tang Dynasty. However, this is the first bi-symmetric layout that can be tested, which is what we often call the central axis. Chang 'an in the Han Dynasty also had two cities, East and West. Chang 'an City in Han Dynasty is located in the northwest suburb of Xi City, with an area of about 36 square kilometers, which is about four times that of Rome in the same period. Chang 'an has 12 city gates and 8 streets, the longest of which is 5500 meters long. Palaces, aristocratic mansions, government offices, ancestral halls and other buildings account for about two thirds of the city's area. The palaces are concentrated in the central and southern parts of the city, including Changle Palace, Weiyang Palace, Guigong Palace, Gong Bei Palace and Mingguang Palace. Weiyang Palace is one of the most famous palaces in the history of China, where many emperors lived and handled state affairs since Emperor Hui of Han Dynasty. Located in the north of the city, the residential area is divided into 160 "Green Lane". The market is in the northwest corner of the city, which is called "Nine Cities of Chang 'an". There are a large number of Shanglin Gardens in the west of the city, including Kunming Pool and Zhangjian Palace. In the south of the city, there is a group of sacrificial buildings built during Wang Mang's period. Chang 'an City in the Han Dynasty changed the pattern of matching large and small cities in the Warring States Period, and concentrated residential areas, industrial and commercial areas and palace areas in one city, which was followed by later capitals.