Longest defensive work ever built

What to remember

Counting walls and trenches, the Great Wall of China spans 21,196.18 km (13,170.70 mi). No defensive work has ever been longer.

It is not one wall but a series of fortifications, built along the historical northern borders of ancient Chinese states and Imperial China against nomadic groups from the Eurasian Steppe. The first walls date to the 7th century BC; they were joined together under the Qin dynasty, and later dynasties kept extending the system. The best-known sections were built by the Ming, from 1368 to 1644, running from Shanhaiguan in Hebei to Jiayuguan in Gansu.

The wall did more than stop armies. Watchtowers, troop barracks, garrison stations and smoke or fire signals made it a guarded line, and it served as a transportation corridor. It also allowed control of movement across the border and the imposition of duties on goods carried along the Silk Road.