Qin Shihuangdi was the emperor who ordered the Great Wall of China to be built. Born in 259 BC, he ruled at the young age of 13 after his father died.
Qin Shihuangdi started building the Great Wall between 220 – 210 BC. Its primary purpose was to protect the country by keeping the northern Mongolian horsemen away, using a structure of bricks and stones. The wall also served as a way to send information. Messages were sent from the watchtowers using smoke signals during the day and bonfires at night. According to an official measurement, the wall is 3,946 miles long. But in 1990, a Chinese walker measured 4,163 miles on his pedometer when he walked along the wall.
Soldiers, political prisoners, and convicts were forced laborers in building the wall. It took around 300,000 people to build it. Several thousand died during construction and were buried onsite. It was a remarkable achievement.
The Great Wall had to be rebuilt multiple times because it was abandoned and neglected often over the years. It was rebuilt 18 times during the Ming dynasty, between 1368 and 1644 AD. The wall is one of most significant engineering accomplishments of all time and remains as one of the Great wonders of the Modern World.
[Source: 100 Great Wonders of the World]