The Great Wall of ChinaThe wall crosses valleys and desert

the great wall 6400km long

The Chinese built n the great wallthousands of years ago

The most famous is the wall built between 220–200 BC by the first Emperor of China

2 to 3 million Chinese died as part of the centuries-long project of building the wall

Mongol raids continued periodically over the years

Towards the end of the Ming Dynasty the Great Wall helped defend the empire against the Manchu invasions that began around 1600

Before the use of bricks the Great Wall was mainly built from Earth or Taiga stones and wood.

The square lookout towers that characterize the most famous images of the wall have disappeared completely

Many western sections of the wall are constructed from mud rather than brick and stone and thus are more susceptible to erosion.