The terrain of Zhongnan Mountain is dangerous and the roads are rugged. There are five big valleys, and the small valleys are more than 100 and hundreds of miles. The "Zuo Chuan" calls Zhongnan Mountain "the risk of Kyushu", and the "history" contains Qinling Mountain as "the obstacle of the world." Song people wrote "Chang'an County Zhi": "Zhongnan Hengyuguan in the south, Qinyu in the west, Lantian in the east, 800 miles apart, the old people said the big mountain, too much outside, Mo like the south."