The Great Wall of China is not one wall at all. It is a network of walls, trenches and watchtowers built and rebuilt over more than two thousand years by different dynasties. If all its sections were laid end to end, they would stretch over 21,000 kilometres – more than half the distance around the Earth.
The earliest walls were built from packed earth around the seventh century BCE, when rival Chinese states defended their borders from one another. In about 220 BCE, the first emperor of a united China, Qin Shi Huang, ordered many of these separate walls to be joined together to protect the north from raiding groups.
The sections that most visitors see today are far younger. They were built during the Ming dynasty, between the fourteenth and seventeenth centuries. Ming builders used bricks and stone, which is why these sections have survived so well. Watchtowers were placed close enough together for soldiers to send signals using smoke by day and fire by night.
The wall came at a terrible cost. Hundreds of thousands of soldiers, prisoners and farmers were forced to work on it, often in freezing mountains or burning deserts. Many died, and stories and songs about their suffering are still told.
Did the wall work? Historians disagree. It slowed down small raids and helped control trade and travel, but determined armies could still break through or simply go around it. Today, its greatest power may be as a symbol – of human effort, of history and of a nation's identity.
