The Great Wall of China more than twice as long as thought

The Great Wall of China is more than twice as long as originally thought, as the first attempt to measure all of its various fortifications found it added up to more than 13,000 miles, built over the course of 13 dynasties.

Major construction of the Great Wall dates to the first emperor of the Qin dynasty (221-206 BC), and was expanded centuries later

Contrary to popular belief, the Great Wall of China is not a single wall, but instead a series of often overlapping defensive fortifications, some brick and others of packed earth, built over the course of nearly 2,000 years, many of which run parallel to each other.

Beginning in 2007, teams of Chinese surveyors fanned out across 15 Chinese provinces to measure every wall, or trace of a wall, they could find.

"This figure (of 13,173 miles) takes into consideration all of the walls that were ever built, even if they are no longer still standing," said Dong Yaohui, the deputy director of China's Great Wall Association.

Previously, the length of the Great Wall had been put at around 5,500 miles: the span of the Ming Dynasty wall whose grey brick fortifications are one of Beijing's most popular tourist destinations.

"The Ming Wall has only been mapped twice, once by the Jesuits in the 1700s under the orders of the Kangxi emperor, and then again in 2006," said William Lindesay, a British expert on the wall.

"Soon after they finished in 2006, the State Administration of Cultural Heritage ordered teams in every province to measure any of the wall that were in their jurisdiction. Thirteen dynasties ordered walls to be built, so this is the sum total of the walls of the other 12.

Of course many may now be fragmented and derelict. The figure is a bit disappointing, I expected it to be higher."

Major construction of the Great Wall dates to the first emperor of the Qin dynasty (221-206 BC), and was expanded centuries later.

A total of 43,721 heritage sites were identified nationwide during the survey, said Tong Mingkang, an official at the State Administration of Culture and Heritage.

However, he added that only 8.2 per cent of the wall built during the Ming Dynasty remains intact, and that almost three-quarters of that is in a poor condition. The effort to map all of the branches of the wall are part of a new initiative to preserve the structure.