Why is the outline of the ancient city of Beijing missing a corner to the northwest?

During the Ming Dynasty in Yuan Wu, Zhu Yuanzhang made Nanjing his capital and renamed most of the area Beiping. From 1368 to 1420, Beijing temporarily lost its status as the capital. In the meantime, the Ming Dynasty moved the north wall of the whole Yuan Dynasty to the south for about 5 miles to the first line of the North Second Ring Road, and only two gates were opened, Anding Gate in the east and Shengli Gate in the west. In this way, the northwest section of the North City Wall passes through the Jishuitan from the northeast to the southwest, separating the place later called Taiping Lake (until Mr. Lao She threw himself into the lake at the beginning of the Cultural Revolution, and was later filled in and converted into a subway depot) from the city. Because of this, it has been explained that it is through the narrowest place on the water surface to facilitate construction. If the whole city wall is slightly to the north, it will be easier to construct, but the accumulated water pools are all in the city, so it is impossible to build a moat with northwest water. In recent years, some scholars have explained from the geomantic theory that the northwest is the dry position, that is, the fierce position, which needs to be destroyed, so it is deliberately folded. 1370, Judy was made the Prince of Yan. 1380, he lived in Beiping, formerly Yuan Longfu. 1399, Judy launched the battle of Jingnan. 1402, he proclaimed himself emperor in Nanjing. From 65438 to 0407, city walls and palaces were built on a large scale. 142 1 year, Yongle emperor Judy changed Beijing to the capital (once called Beijing) and moved the capital to Beijing. Beijing has resumed its capital status.

The result of this large-scale construction is:

The south wall of Dacheng moved southward from Chang 'an Street to Qiansanmen Street, and still opened three gates, namely Zhengyangmen, Dongchongwenmen and Xixuanwumen, and changed the east and west gates to Dongzhimen, Chaoyangmen, Xizhimen and Fuchengmen respectively. There are nine gates in the big city, and then there is the official position of "Nine Magistrates" (slightly equivalent to the current Beijing garrison commander).

The positions of the north wall and the west wall of the imperial city remain basically unchanged. The east wall was slightly expanded eastward, and the north-south waterway (now the first line of North-South Riverside Street) was included in the Imperial City, so water transport vessels could no longer enter the city, so they retreated to Chaoyangmen and ended in Tongzhou. When the south wall moves south to the north of Chang 'an Avenue, you can still see the red Xiao wall. However, the southwest corner is the territory of Daxiong Erji, and the imperial city is accommodated in the temple, and the Xiao wall is built with twists and turns, which makes the imperial city lack the southwest corner.

Miyagi, also known as the Forbidden City, has changed the most. In order to suppress the imperial power of the former dynasty, Yuan Miyagi was completely demolished, instead of capturing the metropolis in Xu Da and burning it and rebuilding it. After the reconstruction, the Forbidden City moved to the south of Yuan Palace, and an earthen mountain was built in the former site of Yuan Yanchun Pavilion, which is now Jingshan Park. Jingshan Park, which is piled up with coal ash in the imperial palace, is not the "town mountain" to suppress the imperial power of the former dynasty and the "backing" of the Feng Shui in the Forbidden City. The layout of the "front hall and back bedroom" in the Forbidden City is clearer. The former dynasty was the Imperial Palace, the Relay Hall and the Jianji Hall, that is, the Hall of Supreme Harmony, the Hall of Zhonghe and the Hall of Baohe, while the later dynasty was the Ganqing Palace, the Jiaotai Palace and the Kunning Palace. On the left and right are the six palaces, followed by the imperial garden. Outside the south gate of the Forbidden City, there are ancestral temples and social altars, namely the Working People's Cultural Palace and Zhongshan Park, which are still "left ancestors and right houses". However, except Di 'anmen to Gulou, Dongsi and Xisi, Chessboard Street to the north of Zhengyangmen (now between Zhengyangmen and Memorial Hall) gradually formed a lively "city facing the front" due to its proximity to the major government offices of the imperial court, and then extended to the main entrance. The "former dynasty and the market outlook" have changed.

Outer cities appeared in Jiajing period. In order to strengthen the defense of Mongolian cavalry in Beijing, especially in the north, the outer city was built on 1553, and 1563 was terminated due to lack of financial resources, and only the southern half was built. This is the origin of the "convex" outline of the ancient city of Beijing. There are three gates in the outer city, Yongdingmen in the middle, Zuo 'anmen (commonly known as self-cleaning gate) in the east, You 'anmen (commonly known as South West Gate) in the west, Refractive Gate (commonly known as Shawo Gate) in the east, Guangning Gate in the west (changed from Daoguang to Guang 'anmen in Qing Dynasty, commonly known as Zhang Yimen), and one gate in the northeast and northwest corners, namely East Gate and Bianxi Gate.

At present, there is a section of Ming city wall site east of Beijing Railway Station, and a park has been built. Now the building on the northeast side of Beijing Railway Station is the southeast corner of the inner city, not the east gate. A small section of Ming city wall was also found in the southwest corner of the original inner city. After the transformation, it was wrapped in a big wall and built a watchtower. However, this provision is wrong. Instead of sticking to the wall, it ran to the top of the wall, which is not the old site of Xibianmen. These two buildings are often misnamed.

Some netizens "Beijing Axis" suggested that it was normal for the central axis of Dacheng in Yuan Dynasty to be inconsistent with that of Miyagi. In the Ming Dynasty, the central axis of Yuan Dynasty was regarded as the central axis of Miyagi and Dacheng, which eventually formed the central axis of Beijing. This makes sense.