皇宫、故宫、紫禁城、博物院是不同时期的四个机构,天安门是这四个机构的大门,又是皇城的正门。北京是都城,因而有四道城垣,即外城、内城、皇城和宫城。北京外城有七座城门,南门称永定门。正阳门是北京内城正门,俗称前门,由城楼及箭楼组成。城楼创建于明永乐十九年(1421),箭楼建于正统四年(1439)。清乾隆四十五年(1780),箭楼毁于火,次年修复;道光二十九年(1849),箭楼再遭火灾,当年兴工修复。光绪二十六年(1900),八国联军进北京,烧毁了城 The Imperial Palace, the Forbidden City, the Forbidden City and the Museum are the four institutions of different periods. Tiananmen is the gate of these four institutions and the main gate of Imperial City. Beijing is the capital, which has four walls, that is, the outer city, the inner city, Imperial City and Miyagi. There are seven gates in Beijing’s outer city, and the south gate is Yongding Gate. Zhengyangmen is the main entrance of the inner city of Beijing, commonly known as the front door, composed of watchtower and watchtower. Watchtower was founded in Ming Yongle nineteen years (1421), Arrow House was built in orthodox four years (1439). Qing Emperor Qianlong forty-five years (1780), arrow tower destroyed in fire, repair the following year; Daoguang twenty-nine years (1849), watchtower and then suffered a fire, then repair work. Twenty-six years Guangxu (1900), the Eight Allied Forces into Beijing, burned the city