A massive survey Spanning 15 provinces, autonomous regions and municipalities in China, the 2012 survey report has set the entire length of the various walls at 21,196.18 kilometres.
This is the first time the complete figure had been released, as a preliminary survey showed the Great Wall that was built during the Ming Dynasty (1368-1644) extended around 8,850 kilometres in total length.
The archaeological survey over the past five years has found and recorded a total of 43,721 heritage sites, including stretches of the wall, defensive works and other structures related to the Great Walls.
The report was released by Tong Mingkang, deputy chief of the the State Administration of Cultural Heritage.
Multiple walls
The Great Wall of China is actually a series of fortifications made of stone, brick and tamped earth, built along an east-to-west line across the historical northern borders of China in part to protect against intrusions by various nomadic groups who lay to the north. Another function would have included border control, allowing the imposition of duties and taxes on goods transported along the Silk Road.
The earliest known constructions date back to the 7th century BCE. The most famous of the wall building periods was between 220–206 BC when the first Emperor of China, Qin Shi Huang created a massive unified barrier, though little of that wall remains.
The wall was massively restructured and repaired during the Ming period, and towards the end of the Ming Dynasty it helped defend the empire against the Manchu invasions that began around 1600.
Under the military command of Yuan Chonghuan, the Ming army held off the Manchus at the heavily fortified Shanhaiguan pass, preventing the Manchus from entering the Chinese heartland.
( via pasthorizonspr.com)