On this day, 753 years ago, on March 28, 1272 (February 27, 1272, the Yuan Dynasty changed Zhongdu to Dadu. On March 28, 1272 (February 27, the ninth year of the Yuan Dynasty) Kublai Khan issued an edict to change Zhongdu of the capital to Dadu (now Beijing) and establish the Ministry of Central Affairs Office here. Metropolis was the political, economic and cultural center of the country at that time. Its layout is: outside the city, there are three floors of Kaocheng, Imperial City and Palace City. The circumference of the outer layer is 28,600 meters, the north and south roads are long and rectangular. There are 11 city gates on all sides: in the east are Guangzhao Gate, Chongren Gate and Qihua Gate; To the south are Wenming Gate, Lizheng Gate and Shuncheng Gate; to the west are Shuoquan Gate, Heyi Gate and Pingze Gate; to the north are Anzhen Gate and Jiande Gate. The Imperial Palace is arranged in three groups on both sides of Qionghua Island and its surrounding lakes. On the west side are the Longfu Official and Xingsheng Palace built by the Crown Prince and the Empress Dowager; The palace on the east bank of the lake belonged to the emperor, and the three palaces were built around them to symbolize the imperial city. The residential area outside the imperial city is divided into 50 squares along neat vertical and horizontal streets. Commercial districts are distributed in three places in the north. This city is a masterpiece of ancient urban architecture in China.