It shows the four major historic periods for Chongqing’s city construction. During the Warring States Period, the State of Qin sent Zhang Yi to build city and fortress at Chaotianmen and Jiangbeizui. During The Three Kingdoms Period, Li Yan and his son built a city on the north bank of the Yangtze River. During the Southern Song Dynasty, Peng Daya built cities of larger scale around Linjiangmen and Jiaochangkou. During the Ming Dynasty, Dai Ding built stone gates on a grand scale, forming the city structure of seventeen city gates.