How long is the Great Wall of China and why was it built?
ONE of the Seven Wonders of the World, The Great Wall of China can be seen from the International Space Station orbiting the earth.
It is one of the greatest engineering feats in the history of the human race.
How long is the Great Wall of China and where is it?
The Great Wall of China is an enormous 13,000 miles - or 21,000km - long.
It is located in northern China, and the most famous section is Great Wall-Badaling.
The wall was granted Unesco World Heritage status in 1987 and has been visited by more than 300 heads of state, including Barack Obama, David Cameron, and Queen Elizabeth.
It has around 10 million visitors each year, possibly more during large events such as the Winter Olympics 2022.
Why was the Great Wall of China built?
China's border walls were first built during the Zhou Dynasty, back in 770 BC.
Then, in 221-207 BC, the First Emperor of Qin commissioned an extension of the wall - to protect his territory from invasion by northern states.
According to historical records, the Chu State first built a "Great Wall" around 676 BC and it turned out to be quite effective in resisting invasions.
Other states then began to build "Great Walls" on the borders of their own territory.
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At the time, they were split into two sections, the Southern Great Walls and the Northern Great Walls.
While both of these defended the areas against invasion, Qin Shihuang, China's First Emperor, united China in 221 BC and ordered the pulling down of the southern Great Walls, but he purposefully kept and linked the northern Walls built by the states of Qin, Zhao, and Yan.
This was to protect them against the threat of invading Huns (the Mongol Empire of the time).
During Han Wudi's reign, in 206 BC, the wall was lengthened into western China, to protect the Silk Road trade.
It was extended into the Yumen Pass and beyond, and this portion of the project took more than 400 years to complete.
The wall is mainly from the Ming Dynasty and is around 20 to 23 feet (six to seven metres) high on average but the tallest section stands at 14 feet.
How long did the Great Wall of China take to build?
In total, the Great Wall of China took more than 2,000 years to build - between 770 BC and 1633 AD.
However, its construction was completed in stages - spanning over several dynasties and leaderships.
The most recent portion was built during The Ming Dynasty.
In 1368, Hero General Qi Jiguang ordered for the Great Wall to be rebuilt around the country's capital of Beijing.
The project was finally completed in 1644.