While not really visible from outer space, the Great Wall of China is still an amazing feat of architecture. Although called the "Great Wall", the 3,700 mile (6,000 kilometers) long structure actually consists of several massive walls, some as tall as 29.5 feet (9 meters). In some places there are as many as three separate walls spaced 50 miles or more apart, in others there are gaps filled by mountainous terrain.
The earliest stretches of wall were built during the Warring States period in China (500-221 BC). It was the Qin Dynasty (221-206 BC) leader Shi-huangdi who began consolidating and strengthening the walls during his forced unification of what was to become China. The Silk Road opened up traffic between the east and west about this time, and it is perhaps likely that the infusion of barbarians from the west that made building the wall so compelling.
Yang, Xiaoneng. 2004. Chinese Archaeology in the Twentieth Century: New Perspectives on China's Past. Yale University Press, New Haven.
This glossary entry is part of the Dictionary of Archaeology.