The Ming Great Wall at Sanguankou

　　Yinchuan is situated in the northwestern frontier of China. During the Ming Dynasty, Mongolian tribes such as the Tatars and Oirats frequently invaded through Chimu Pass (present-day Sanguankou) in the Helan Mountains from the Alxa Plateau in Inner Mongolia, advancing straight into the plains. To strengthen border security, the Ming rulers built the Great Wall (referred to as the "frontier wall" at the time) and established fortifications at Sanguankou, making it one of the “Four Key Defenses” of ancient Yinchuan.

　　The Ming Great Wall at Sanguankou is located over 40 kilometers west of Yinchuan in the southern part of the Helan Mountains. This pass marks the border between Ningxia and Alxa Left Banner in Inner Mongolia, with the Yinchuan–Bayanhot Highway passing through it. Remnants of the Great Wall can be seen at the pass. The three passes—namely the First Barrier, Second Barrier, and Third Barrier from east to west—are collectively referred to as the Three Passes by later generations. The area features winding mountain ranges and rugged, dramatic terrain. Originally, a strategic pass was built in the valley sandwiched between two mountains.

　　 Ningxia, Yinchuan