Great Wall of China

The Great Wall of China is a giant series of walls and forts in northern China. It was built over many centuries to protect China from invaders coming from the north. The wall winds across mountains, deserts, and grasslands. Today, parts of it are over 2,000 years old. Other parts are only about 400 years old.

The first walls were built more than 2,200 years ago. China's first emperor, Qin Shi Huang, ordered them built around 220 BCE. He wanted to keep out nomadic tribes that raided Chinese farms and towns. To save time, his workers connected older walls that smaller kingdoms had already built. Hundreds of thousands of soldiers, farmers, and prisoners did the building. Many of them died on the job and were buried near the wall.

Later rulers kept adding to it. The Han dynasty stretched the wall west into the desert to protect the Silk Road, the trade route that carried goods between China and the rest of Asia. But most of the wall people see today was built much later, during the Ming dynasty, between 1368 and 1644. The Ming rulers used stone and brick instead of packed dirt. Their wall was stronger and taller, with watchtowers every few hundred yards.

The Ming wall is huge. It runs about 5,500 miles from the Pacific coast to the deserts of western China. That is longer than the distance from New York to Los Angeles and back again. In some places it stands 25 feet tall and 15 feet wide at the top, wide enough for soldiers to ride horses along it. Towers held lookouts who lit signal fires to warn of attacks. A fire at one tower could pass a warning hundreds of miles in a single day.

Did the wall actually work? Historians still argue about this. The wall did slow down small raids and force invaders into narrow passes where Chinese soldiers waited. But big armies got through anyway. In 1644, a Chinese general opened the gates and let the Manchu army from the north march in. The Manchus took over China and started the Qing dynasty. The wall had not stopped them.

You cannot really see the Great Wall from space with your eyes alone, even though many people repeat that claim. Astronauts have said the wall is too narrow and too close in color to the land around it. What you can see, when you visit, is something else entirely: a stone river of human work climbing over mountains as far as the eye can follow.