The Great Wall of China is one of the most amazing piece of architecture and the most ambitious building project ever attempted in the history of mankind. Construction of this formidable defensive structure, built to ward off invasion and to protect the Chinese Empire, goes back by more than two thousand years to the the 7th century BC during the Chunqiu period. Especially famous is the wall built between 220–206 BC by the first Emperor of China, Qin Shi Huang. Little of that wall remains. Since then, the Great Wall has on and off been rebuilt, maintained and fortified. Construction continued up to the Ming dynasty (1368–1644), when the Great Wall became the world’s largest military structure.