The Great Wall is a series of fortifications spanning from the Bo Hai in the east to the Gobi Desert in the west.
The ancient Chinese built walls for protection. Because China does not have natural boundaries in the north, Emperor Qin Shihuangdi started connecting many of these walls to prevent raids by the nomadic Xiongnu.
Construction of the Wall began under the Qin dynasty (221-206 BC) but much of the Wall we see today comes from the Ming period (1368-1644).
The World Monuments Fund listed the Wall as one of the World's 100 Most Endangered Sites in 2002. The Chinese government subsequently enacted laws to protect it.
Legend has it that the Great Wall of China can be seen from the moon. After Apollo 12 landed on the moon in 1969, astronaut Alan Bean remarked that no man-made objects on earth were visible.
