How many Nine Dragon Walls are there in China?

Jiulong wall is a kind of shadow wall. That is, the wall outside the building facing the gate serves as a barrier, commonly known as zhaobi, zhaobi. Shadow wall evolved from "hiding". The door is "hidden" and the door is "avoided", so it is used to being called the screen wall in the future.

At present, there are four Nine Dragon Walls in China (one in Datong City, Shanxi Province and one in Wuxi City, Jiangsu Province). Among them, the Forbidden City, the Nine Dragon Walls in Datong, Shanxi Province and the Nine Dragon Walls in Beijing Beihai Park are collectively called the "Three Great Nine Dragon Walls in China".