Introduction to Shangjin Ancient City: China has a long history of city building, which originated in the Xia Yu period. The ancient book "Natural History" says: "Yu made the city, the strong attacked, the weak defended, and this is the beginning of the city". The Spring and Autumn Annals of Wu and Yue highly summarized the role of the city: "Build a city to defend the monarch, and build an outline to guard the people".