Introduction to the Zhongdu ruins of the Yuan Dynasty: The Yuan Dynasty built four capitals successively, the capital Harahorin (now Mongolia), Dadu (Beijing), Shangdu (Blue Banner) and Zhongdu (Zhangbei). During the Liao, Jin and Yuan Dynasties, Zhongdu was a transportation hub connecting Mobei to the north, the Western Regions to the west, and the Central Plains to the south. It was an important military base and was also a holy place for summer hunting for the royal relatives at that time. The Yuan Zhongdu ruins are located in Mantouying Township, Zhangbei County. It is composed of three layers of inner, middle and outer cities, namely the outer city, the imperial city and the palace city.