Introduction to the Baiyangyu Great Wall: It was built by the Yan State during the Warring States Period and restored and reinforced during the Ming Dynasty. There are 21 towers and the well-preserved Great Wall is 4,552 meters long. The marble Great Wall here is about 1.5 kilometers long, 10 meters high and 5 meters wide. Most of the foundations of the watchtowers at the bottom of the city are marble. It is very rare in Wanliguan Mountain and is the essence of the Great Wall.