What's so particular about the courtyard gate?

The gate of the quadrangle is exquisite in geomantic omen: the courtyard facing south is in the right position, and its gates are all open in the southeast corner of the courtyard. "Zhouyi, Art Theory, Kun chisels Li Lun, Kun, Xun and Min" points out: "Xun is a damper, a local resident, connecting heaven and earth." The location in the gossip is a ventilated place, just like the window of a house, which can connect the vitality of heaven and earth. In addition, the traditional buildings in China pay special attention to the smooth drainage. Siheyuan is surrounded by houses with a yard in the middle. So how is the rain discharged when it rains? Because the terrain of quadrangles is often high in the northwest and low in the southeast, water flows from the northwest to the southeast. In this way, the drainage function of the southeast corner is highlighted. From the point of view of drainage, it is necessary to open the courtyard gate in the southeast corner. Not only that, Beijing's drainage system also embodies this concept. During the Ming and Qing Dynasties, the water system in Beijing was from Jishuitan in the northwest to Tongjiang in the southeast. During the Ming and Qing Dynasties, the Jinshui River in the Forbidden City in Beijing entered the water from the tunnel on the west side of Shenwumen and went out to the southeast of Luanjiaku.