外城七门外城与内城相接，环抱内城南部，故亦名南城，外城始建于明嘉靖三十二年（１５５３）。明朝中期因蒙古骑兵屡犯京郊，威胁城防，为了加强对都城的保卫，原计划环内城四面一律加筑外垣，以形成对皇宫的多层保护圈。但当时因耗资巨大，财力匮乏，仅建成环抱南郊之部分，? Outside the city seven outer city and the inner city phase, embracing the southern city, it is also known as South City, the outer city was built in the Ming Jiajing thirty-two years (1553). In the mid-Ming period, the Mongolian cavalry repeated intimidation to the suburbs and threatened the defense of the city. In order to strengthen the defense of the capital, the original plan was to create a multi-layered protection ring for the palace. However, due to the huge cost and lack of financial resources, only the part encircling the southern suburbs was completed.