First of all, in ancient times, urban planning generally conformed to the four gods, and the specific explanation is as follows:
Because it is "in the south", in geomantic omen, Qinglong, Baihu, Suzaku and Xuanwu are often used to indicate orientation. For example, The Book of Burial says, "Take the dragon on the left, the white tiger on the right, the suzaku in front and the Xuanwu in the back." "Ten Books of Yangzhai" said: "Anyone who has running water on the left side of the house is called Qinglong; There is a long road on the right, called white tiger; There is a sweat pool in front, called Suzaku; There is a hill behind, called Xuanwu, which is the most expensive place. " Thus, Qinglong, Baihu, Suzaku and Xuanwu became the names of the four gods in Feng Shui. In fact, in ancient times, people had a clear concept of orientation god. Such as the Book of Rites. "Quli Shang" said: "OK, rosefinch in front and then Xuanwu, left Qinglong right white tiger." The names of the four gods represent the names of the four gods, forming four celestial phenomena, east, west, north and south. So, Huai Nan Zi. "Astronomical Training" said: "The most expensive god is Qinglong." Qinglong, Baihu, Suzaku and Xuanwu, as the gods of the four directions, were later respected by Taoism and had a wide influence on China culture.
Four gods, such as Qinglong and Baihu, are orientation gods, and each town guards the city, town and house. Those who meet the following conditions can be called "land of four gods" or "land of four spirits". Its conditions are "Xuanwu bows its head, Suzaku dances, Qinglong winds and white tigers tame." That is to say, the peak in the direction of Xuanwu looks down, and the peak in the direction of Suzaku will come to sing and dance, the Qinglong Mountain on the left is constantly undulating, and the White Tiger Mountain on the right is vigorous. Such an environment is a "land of geomantic omen".
2. Feng Shui in Nanjing
I have never been to Nanjing myself. I found all the following online.
Nanjing City faces south with its back to the north. In the north of the city, there is a Jilong Mountain, which the former Feng Shui masters thought was a backer. It's actually just a small mound 60 meters high. Behind Jilong Mountain is the vast Xuanwu Lake, and further north is Hongshan in the northern suburbs. Hongshan has a larger area, but it is more than 60 meters high like Jilong Mountain. In fact, it is just a small hill. Three kilometers north of Hongshan Mountain, there is a shogunate mountain of 150 meters. Passing through the north of the Shogun Mountain, you can immediately overlook the mighty Yangtze River. This is the terrain in the north of Nanjing.
The most basic principle of geomantic omen is "managing people and managing wealth". "Landscape" is just a concept of orientation. "Mountain" represents the back and dominates the health and prosperity of the population. The backer of feng shui should be vigorous and powerful, and the most taboo is to bring gas. "Water" represents the front, dominates the cause and wealth income, and should be wider than water, and the most taboo is small. But Nanjing's backers are scattered and weak, which is not enough to support such a big city. Even more deadly, all the backers are backed by the Yangtze River, and there are no mountains connected, so they can't get the support of Long Mai; Xuanwu Lake, which is larger than all the backers, completely blocks the dragon gods in the mountains of Nanjing, because the geomantic gods are "scattered in the wind and scattered in the water". After being banned by Xuanwu Lake, even a little bit of backing and atmosphere were consumed, forming a completely empty Feng Shui shape.