Great Wall of China

The **Great Wall of China** (, literally "ten thousand *li* long wall") is a series of fortifications in China. Chinese emperors and dynasties built the wall (and joined together existing walls) to protect the north of their empire from enemy attacks. In total, the wall stretches . 

The first walls were built in the 7th century BCE. Later, during the Qin dynasty (which ruled China from 221 BCE to 206 BCE), these walls were connected. Later dynasties continued construction on the wall system. Between the 3rd century BCE to the 17th century CE, it was under construction continuously. 

The Ming dynasty (which ruled from 1368 CE to 1644 CE) built the best-known sections, which stretch between 4,000 and 5,500 kilometers (2,500 and 3,400 miles). It is a UNESCO World Heritage Site. 

## History 
### Beginnings 
Great Wall of Qi was started in 685 BC. The state of Qi made a fortified wall for protection against the Southern states Ju and Lu and later from the kingdom Chu.

The state of Yan built walls during the rule of King Zhao of Yan (311–279 BC).

The state of Zhao built walls during 325–299 BC, during the rule of king Wuling of Zhao.

### Qin dynasty 
The First Emperor of China, Qin Shi Huang also called Shi Huangdi, started the Qin Dynasty. The Xiongnu tribes in the north of China were his enemies. The land in some parts of China is easy to cross, so Qin Shi Huang started building the Great Wall to make it more difficult for the Xiongnu to invade China.

The most famous part of the Great Wall was built between 226 and 200 BC by the first Emperor of China, Qin Shi Huang (Qin Pronounced as Chin), during the Qin Dynasty. 

Walls on the periphery of the Northern states Yan, Zhao, and Qin became linked together, because all those states came under the rule of emperor Qin Shi Huang during his rule (221–206 BC).

By 212 BC, the wall went from Gansu to the coast of South Manchuria.

### Expansion 
Other dynasties in China continued to build and lengthen the Great Wall. The Han, Sui, Northern and Jin Dynasties all repaired, rebuilt or expanded it. Their goal was to protect China from Mongol invasions from the north. 

During the Ming Dynasty (1368 CE - 1644 CE), Chinese leaders built between 4,000 and 5,500 kilometers of new wall (2,500 and 3,400 miles). They are made of mortar, rocks, adobe bricks, and dirt.

## Visibility from space 
A astronaut named William Pogue was able to see the wall from a Low Earth Orbit (300–530&nbsp;km above Earth), but only with binoculars and a lot of practice. Another astronaut, Neil Armstrong, said that on the Moon, it was very clear that the wall was not visible. The Great Wall has shown up in some photos taken from space, but scientists are sure it is not possible for astronauts to see the wall without binoculars.

## Gallery

File:"The First Mound"--the west end of the Great Wall.jpg|The First Mound at the Jiayuguan Pass Pass in Gansu
The Journey of Discovery Beijing (6962643268).jpg|Near Jiayuguan
明长城 - panoramio (1).jpg|Near Yinchuan in Ningxia
榆林市的明长城遗迹 - panoramio.jpg|In Yulin, Shaanxi
GreatWall 2004 Summer 1A.jpg|In Badaling's Yanqing District in Beijing
File:Juyongguan Great Wall.jpg|In the Juyongguan area of Beijing
File:Gubeikou Gate.jpg|The gate at the wall in Gubeikou, Beijing
File:Great Wall at Simatai overlooking gorge.jpg|In Simatai, Beijing
File:MutianyuGreatWallWildSection.JPG|In Mutianyu, Beijing
File:Great wall stops in see.jpg|At Shanhaiguan
File:Great Wall of China.jpeg|At Badaling in 1979

## Sources 
* Di Cosmo, Nicola (1999). "13. The Northern Frontier in pre-Imperial China". In Loewe, Michael; Shaughnessy, Edward (editors). The Cambridge History of Ancient China. Cambridge: Cambridge University Press. ISBN 978-0-521-47030-8.
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