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Great Wall of China
Fragment of the Old Great Wall of China
CC gin_e at Flickr.com
This is a fragment from the old Great Wall of China, outside Yulin City, built by by the first Emperor of China, Qin Shi Huang 220–206 B.C. The Great Wall was built to protect from northern invaders. There were several walls built over the centuries. The Great Wall that we are more familiar with was built during the Ming Dynasty in the 15th century.
The length of the wall has been determined to be 21,196.18km (13,170.6956 miles), according to BBC: China's Great Wall is 'longer than previously thought'.