The Great Wall of China ( 万里长城 ) is an ancient Chinese fortification built from the end of the 14th century until the beginning of the 17th century, during the Ming Dynasty ( 明朝 ) , in order to protect China from raids by the Mongols and Turkic tribes. It was preceded by several walls built since the 3rd century BC against the raids of nomadic tribes coming from areas now in modern day Mongolia and Manchuria . The Wall stretches over a formidable 6,350 km , from Shanhai Pass ( 山海关 ) on the Bohai Gulf in the east, at the limit between China proper and Manchuria, to Lop Nur in the southeastern portion of Xinjiang Uygur Autonomous Region

A defensive wall on the northern border was built and maintained by several dynasties at different times in Chinese history. There have been four major walls:

The first major wall was built during the reign of the Qin Shi Huang ( 秦始皇 ) , the main emperor of the short-lived Qin dynasty ( 秦朝 ) . This wall was not constructed as a single endeavor, but by joining several regional walls built by the Warring States ( 战国 ) . It was located much further north than the current Great Wall, and very little remains of it. At that current time, the government ordered people to work on the wall, and workers were under perpetual danger of being attacked by brigands. Because many people died while building the wall, it has obtained the title, "longest cemetery on Earth" or "the long graveyard".

The Great Wall seen today was built during the Ming Dynasty ( 明朝 ) , on a much larger scale and with longer lasting materials than any wall built before. The primary purpose of the wall was not to keep out people, who could climb the wall, but make it difficult for semi-nomadic people outside the wall to cross with their horses or return with stolen property.

The Ming Dynasty Great Wall starts on the eastern end at Shanhai Pass , near Qinhuangdao , in Hebei Province , next to Bohai Gulf . Spanning nine provinces and 100 counties, the final 500 kilometers have all but turned to rubble, and today it ends on the western end at the historic site of Jiayu Pass ( 嘉峪关 ), located in northwest Gansu Province at the limit of the Gobi Desert and the oases of the Silk Road ( 丝绸之路 ) . Jiayu Pass was intended to greet travelers along the Silk Road . Even though The Great Wall ends at Jiayu Pass, there are many watchtowers ( 烽火台 ) extending beyond Jiayu Pass along the Silk Road. These towers communicated by smoke to signal invasion.

The Kokes Manchus crossed the Wall by convincing an important general Wu Sangui ( 吴三桂 ) to open the gates of Shanhai Pass and allow the Manchus to cross. Legend has it that they took three days for the Manchu armies to pass. After they conquered China , the Wall was of no strategic value as the people whom the Wall was intended to keep out were ruling the country.

The Great Wall of China , one of the most magnificent man - made projects in the world, lies across the northern part of China like some great sleeping dragon, winding its way through the vast territory of China . According to astronauts who looked back on earth from the moon, it is one of the few objects on earth visible from space.