The site of Chang'an City, Han Dynasty, is the starting point, birthplace and decision-making place of the ancient Silk Road. It has the reputation of "East Chang'an, West Rome". It is also called the world's earliest international metropolis. It was the largest city in the world at that time. The longest used in ancient China, the most in the Dingdu Dynasty, and the most rich in relics. The Han Chang'an City site is the physical data of the world to understand ancient Chinese culture.