The Great Wall of China is a series of stone and earthen fortifications in , built, rebuilt, and maintained between the 5th century BC and the 16th century to protect the northern borders of the Chinese Empire during the rule of successive dynasties.
Yanmen Guan is part of the Outer Great Wall in Shanxi Province, just north of Taiyuan, and forms a chokepoint with Ningwu Guan as the central linchpin (and garrison base) and Pian Guan as the westernmost stronghold.