What is the difference between the functions of ancient cities and those of modern cities?

Function of the city: From the Zhou and Qin Dynasties to the Tang Dynasty, the city was a political center and a military center, with a small commercial trade and market scale. After the Song Dynasty, the economic function of the city was greatly strengthened. During the Ming and Qing Dynasties, the economic functions of cities became more prominent. Reasons: improvement of production tools and production technology; With the development of agriculture and handicrafts, the degree of commercialization of agricultural products has improved; The development of commodity economy; The concern of the ruling class.