明清时期,人们从南城进京,迎接他们的第一个视点就是永定门(图1)。历史上永定门包括城楼、箭楼和瓮城三部分,南部有护城河拱卫。永定门是中轴线的南端,当你从永定门走进之后,遇到的第一个视点是天桥,它是皇帝到天坛和先农坛祭祀的必经之地。从天桥上走下来之后,迎面你会看到一个非常繁华的街市,这就是前门大街了。从永定门到前门,这里住的都是平民百姓,尤其前门大街的胡同 Ming and Qing Dynasties, people from Nancheng to Beijing, to meet their first point of view is the Yongding Gate (Figure 1). Yongdingmen history, including the watchtower, watchtower and Urn three parts, the southern moat arch guard. Yongding Gate is the southern end of the central axis. When you walked in from Yongdingmen, the first point of view encountered was the flyover, which was the place where the Emperor sacrificed to the Temple of Heaven and Xiannong altar. After walking down the bridge, you will see a very busy downtown, this is the front door of the street. From Yongding Gate to the front door, where to live are all ordinary people, especially the front alley