The Great Wall of China is a series of
fortifications
made of stone, brick, tamped earth, wood, and other materials,
generally built along an east-to-west line across the historical northern
borders of China
in part to protect the Chinese Empire or its prototypical states against
intrusions by various nomadic groups or military incursions by various warlike
peoples or forces. Several walls were being built as early as the 7th century
BC; these, later joined together and made bigger and stronger, are now
collectively referred to as the Great Wall.[4]
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
enhanced; the majority of the existing wall was reconstructed during the Ming Dynasty.
Other purposes of the Great Wall have
included border controls, allowing the imposition of duties on goods
transported along the Silk Road, regulation or encouragement of trade
and the control of immigration and emigration. Furthermore, the defensive
characteristics of the Great Wall were enhanced by the construction of watch
towers, troop barracks, garrison stations, signaling capabilities through the
means of smoke or fire, and the fact that the path of the Great Wall also
served as a transportation corridor.
The Great Wall stretches from Shanhaiguan in the east, to Lop Lake
in the west, along an arc that roughly delineates the southern edge of Inner Mongolia.
A comprehensive archaeological survey, using advanced technologies, has
concluded that the Ming walls measure 8,850 km (5,500 mi). This is
made up of 6,259 km (3,889 mi) sections of actual wall, 359 km
(223 mi) of trenches and 2,232 km (1,387 mi) of natural
defensive barriers such as hills and rivers. Another archaeological survey
found that the entire wall with all of its branches measure out to be
21,196 km (13,171 mi).
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