how many kilometers of great wall of china
8,850 km 21,196 km
title: Great Wall of China text: such. The 493 "Book of Song" quotes the frontier general Tan Daoji referring to "the long wall of 10,000 miles", closer to the modern name, but the name rarely features in pre-modern times otherwise. The traditional Chinese mile (, "lǐ") was an often irregular distance that was intended to show the length of a standard village and varied with terrain but was usually standardized at distances around a third of an English mile (540 m). Since China's metrication in 1930, it has been exactly equivalent to , which would make the wall's name describe a distance of . However, this title: Great Wall of China text: Great Wall of China 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 to protect the Chinese states and empires against the raids and invasions of the various nomadic groups of the Eurasian Steppe with an eye to expansion. Several walls were being built as early as the 7th century BC; these, later joined together and made bigger and stronger, are collectively referred to as the Great Wall. Especially famous is the wall built in 220–206 title: Great Wall of China text: means of smoke or fire, and the fact that the path of the Great Wall also served as a transportation corridor. The frontier walls built by different dynasties have multiple courses. Collectively, they stretch from Dandong in the east to Lop Lake in the west, from present-day Sino-Russian border in the north to Qinghai in the south; along an arc that roughly delineates the edge of Mongolian steppe. A comprehensive archaeological survey, using advanced technologies, has concluded that the walls built by the Ming dynasty measure . This is made up of sections of actual wall, of trenches and of title: Great Wall of China text: Beyond Jiumenkou, an offshoot known as the Liaodong Wall continues through Liaoning province and terminates at the Hushan Great Wall, in the city of Dandong near the North Korean border. In 2009, 180 km of previously unknown sections of the wall concealed by hills, trenches and rivers were discovered with the help of infrared range finders and GPS devices. In March and April 2015 nine sections with a total length of more than , believed to be part of the Great Wall, were discovered along the border of Ningxia autonomous region and Gansu province. Before the use of bricks, the title: Great Wall of China text: with concrete. The work has been much criticized. One of the earliest known references to the myth that the Great Wall can be seen from the moon appears in a letter written in 1754 by the English antiquary William Stukeley. Stukeley wrote that, "This mighty wall of four score miles [130 km] in length is only exceeded by the Chinese Wall, which makes a considerable figure upon the terrestrial globe, and may be discerned at the Moon." The claim was also mentioned by Henry Norman in 1895 where he states "besides its age it enjoys the reputation of being the