The Great Wall of China is a series of fortifications made of stone brick tamped earth wood and other materials generally built along an easttowest 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 [ссылка] walls were being built as early as the 7th century BC these later joined together and made bigger stronger and unified are now collectively referred to as the Great WallnOther 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.nThe 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 8850 km 5500 mi.