How Long Is the Great Wall of China?

What do China's official surveys say about the wall's length?

The official figures come from a national survey that China's State Administration of Cultural Heritage organized in 2006 and describes as the most comprehensive and systematic survey of the wall "since the founding of the New China".^[1] Field work ended in December 2010, and the agency released its conclusions in 2012.^[1] The total length of walls and trenches came to 21,196.18 km.^[1]

The survey identified 43,721 separate remains.^[1] They include 10,051 wall sections, 1,764 trench sections, 29,510 single structures, and 2,211 passes and fortresses.^[1]

An earlier stage of the work measured only the wall of the Ming dynasty.^[3] In April 2009, after a two-year investigation, the heritage agency and the State Bureau of Surveying and Mapping announced that the Ming wall is 8,851.8 km long.^[3] Of that, 6,259.6 km is built wall, 359.7 km is trench, and 2,232.5 km is natural barrier such as hills and rivers.^[3]

UNESCO, which lists the wall as a World Heritage site, uses a rounded figure of more than 20,000 km.^[2] For comparison, Earth's circumference is roughly 40,075 km, so the survey total is more than half of that distance.^[1][8]

• All periods21,196.18 km
• Ming dynasty8,851.8 km
• Jin dynasty trench4,010.48 km
• Qin and Han dynasties3,680.26 km
• Spring and Autumn, Warring States3,080.14 km

Source: State Administration of Cultural Heritage of China, published by the UNESCO World Heritage Centre [1]

The chart uses the lengths in the heritage agency's report to UNESCO, which gives no length for walls of other periods, such as the Western Xia.^[1]

Is the Great Wall one continuous wall?

Many people picture the Great Wall as one huge wall, but it is a system of walls and military works.^[4] The survey covered walls from several periods, along with watchtowers, trenches, passes, fortresses and beacon towers.^[1] The Ming wall alone has a main line and branches in Hebei, Shanxi and other provinces.^[1]

Beacon towers formed a warning system. According to a 2008 China Today article, soldiers lit beacons when an attack was reported, and the alarm was relayed through the towers until it reached military headquarters in the capital.^[4]

Sources describe the end points differently.^[2][3] UNESCO says the wall begins in the east at Shanhaiguan in Hebei province and ends at Jiayuguan in Gansu province.^[2] The survey found that the Ming main line starts at Hushan (Tiger Mountain) in eastern Liaoning and runs west to Jiayu Pass in Gansu.^[1][3]

Who built the Great Wall, and when?

Many states and dynasties built the wall, not one ruler.^[1][2] The oldest remains in the survey date from the Spring and Autumn and Warring States periods.^[1] They total 3,080.14 km, and most were built with debris or rammed earth.^[1]

Sources give different starting points.^[1][2][4] A 2008 China Today article says the southern state of Chu began building the wall in the 7th century BC, when rival states were competing for power.^[4] The heritage agency speaks of a history of more than 2,400 years.^[1] UNESCO's summary counts continuous building from the 3rd century BC to the 17th century AD.^[2]

After the Qin dynasty united the country in 221 BC, the walls of the former northern states were linked.^[4] UNESCO dates this joining to about 220 BC, under Qin Shi Huang.^[2] The linked sections had belonged to the states of Yan, Zhao and Qin.^[1]

The Han dynasty wall ran east to west, from eastern Liaoning to Yumen Pass in Gansu.^[1] Han beacon towers continue from Yumen Pass as far as Aksu in Xinjiang.^[1] Remains from the Qin and Han dynasties total 3,680.26 km.^[1] The Jin dynasty added a defensive trench system that is 4,010.48 km long.^[1]

Building went on until the Ming dynasty (1368–1644), by which time the wall had become the world's largest military structure.^[2] The Ming sections are the best preserved.^[1][3]

What is the Great Wall made of?

Builders mostly used materials found nearby.^[1][5] Apart from some masonry sections, most of the wall was built with rammed earth and local materials.^[1] Rammed earth is natural soil that has been packed down hard.^[5] A 2024 study of the wall at Shanhaiguan describes how several workers lifted a rammer and dropped it to press the soil into a dense mass.^[5]

The Qin and Han walls were built mainly with earth and stones, and some sections in western Gansu used reed, rose willow and sand.^[1] In the Ming period, eastern sections were built mainly with bricks and stone, while western sections were mainly rammed earth.^[1]

The Ming wall at Shanhaiguan is mainly brick on the outside and rammed earth on the inside.^[5] Historical records cited in the same study say that glutinous (sticky) rice pulp and lime were added to some sections there, which made the rammed earth stronger.^[5] The study adds that little of the rice paste and lime remains after long weathering.^[5]

Can you see the Great Wall from space?

Not with the naked eye, according to NASA.^[6] The agency says the wall generally is not visible to the unaided eye from low Earth orbit, and it certainly is not visible from the Moon.^[6] The idea that it could be seen from the Moon dates back to at least 1938.^[6]

Yang Liwei, China's first astronaut, said in a television interview that he did not see the Great Wall from space, the Xinhua News Agency reported on October 17, 2003.^[7]

NASA explains that the wall is very hard to pick out in astronaut photographs because its materials are similar in color and texture to the land around it.^[6] A photo taken from the International Space Station by station commander Leroy Chiao on November 24, 2004, with a 180mm lens, was found to show small sections of the wall, and NASA called it the first confirmed photo of the wall.^[6] Chiao said he did not see the wall himself.^[6]

UNESCO's listing still describes the wall as the only work built by human hands that can be seen from the Moon, which NASA's statement contradicts.^[2][6]