A vast system of fortifications built across the northern…

A vast system of fortifications built across the northern frontiers of East Asia to deter nomadic raiders from the steppe. Earlier rammed-earth barriers were begun under the first Qin emperor, but most surviving brick and stone sections date from the Ming dynasty. Watchtowers, garrison forts and beacon platforms let smoke signals travel quickly. Badaling and Mutianyu draw crowds near Beijing, and the eastern end meets the Bohai Sea at Shanhaiguan.

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