Located at the northern border of Shaanxi Province, Yulin was always the point of battle between the central government and the northern nomad in ancient times. Therefore, walls of many dynasties have passed here, such as the walls of the Warring States Period (476 BC - 221 BC), the Qin Dynasty (221 BC - 207 BC), the Sui Dynasty (581 - 618), and the Ming Dynasty (1368 - 1644). Zhenbeitai Fort, the No. 1 fortress of Chinese Great Wall, is also situated here, connected by the Ming-dynasty wall from the east the west sides.