Were City Walls Essential for Ancient Chinese Cities?——Research on the Wall-Building Activities and Urban Morphology in Sichuan and Chongqing Regions in the Tang and Song Dynasties

The policies on constructing capital cities in Sichuan and Chongqing regions had been changed from the Tang Dynasty to the Song Dynasty.In brief,the government didn't attach much importance to building walls surrounded around the capital cities in the early and middle Tang Dynasty.The walls of most capital cities were newly built or rebuilt in late Tang and Five Dynasties.The government assumed a passive attitude towards the city wall construction during the Northern and Southern Song Dynasty.In sum,these policies differed according to time,situation,place and magistrates,and the opinions that consider tradition Chinese capital cities the walled cities was not strictly accurate.