The capital of the Tang Dynasty moved to Chang 'an. Why are most of the tombs of the Tang Dynasty buried in Xianyang?

In geomantic omen, to the north of Weihe River, there are nine zhangs in Shan Zhinan, and the mountains and rivers are all sunny, so it is called Xianyang, the land of geomantic omen, and the descendants are prosperous and solid in Guo Bang; Geographically, Xianyang, also known as Xianyang Plain, is a highland with large area and deep soil layer, which is suitable for building tombs. Politically, it is very close to Tang Dou, and the dead will not be buried directly in the capital, which is inappropriate and there is no such place. Xianyang, a hundred miles away, is just right.