In case you need a refresher on one of the 7 Wonders of the Ancient World, the Great Wall of China, which ranged from 5,500 to 13,171 miles (depending on various archeological studies), was built to protect the Chinese Empire from invading countries and nomadic groups. The Jiayuguan or Jiayu Pass (pictured), located in northern China, is one of the Great Wall’s best-preserved military fortifications. The series of gates and turrets, built of mud bricks, was feared by invaders and the Chinese alike: When citizens were banished from the empire, they were pushed out through Jiayuguan’s gates.
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