Located 4 kilometers west of Jiayuguan city on the northwest part of Gansu Province, Jiayuguan is the western end of the Great Wall of the Ming Dynasty as well as the most magnificent and best-preserved pass among the over thousand passes along the Ming Great Wall, known as "Impregnable Pass Under Heaven". It took 168 years (1372-1539) to build this strategic outpost.
Jiayuguan Pass, located at the narrowest ravine of Hexi Corridor is made up of an inner city, wengcheng (barbican entrance to the city), luocheng (outer round defensive wall), outer city and moat. It a multi-tier defensive works. Its western outer wall extends southward to the bank of Taolai River at the foot of Qilian Mountain, and its northern end links with a hidden wall going halfway up the Heishan Mountain. Jiayuguan Pass is entrenched right in the ravine sandwiched in between two high mountains. So it reputed as Impregnable Pass Under Heaven where one defender can ward off the attack by ten thousand foes.
The inner city, standing right at the center of the Pass, is surrounded by 6 meter-high hardened loess as the base plus 3 meter-high brick wall on the top. 1.7 meter-high brick buttress aligned with crenels and lookout holes are built on top of the wall. Between crenels of the western wall there are notches for lamps. Beneath the notches, are slanting openings for shooting. The city has four corner towers, and a gate tower in the middle of each of the two north to south walls. The eastern and western gates are protected by wengcheng (barbican entrance), which connects with the inner city in a zigzag way. Once the enemy enters the wengcheng, he will find himself like a turtle in a jar waiting to be caught.