Jiayuguan is where the Great Wall ends: the westernmost fortress of the Ming line, built in 1372 to guard the narrowest point of the Hexi Corridor between the Qilian mountains and the Black Mountain desert. For centuries, exiles and traders passing its west gate were formally leaving China.
The fort itself is a magnificent stack of rammed-earth walls and triple gate towers with snow peaks behind — the far end of the same wall you may have walked near Beijing, in a completely different landscape. Add the Overhanging Wall climbing its black hillside and the First Beacon Tower crumbling above a river gorge, both on the combo ticket, for the full end-of-empire effect.