Great Wall

Presenter: Muzhi Liu

Numbers

• Built, rebuilt, and maintained between the 500 BC and the 1600s.

• world's longest human-made structure, stretching over approximately 6,400 km (4,000 miles). To make a comparison, Mississippi river is 2,320 miles long

• largest human-made structure ever built in terms of surface area and mass.

• 7.8 meters (25.6 ft) high and 5 meters (16.4 ft) wide.

Interesting Facts

• Original use is mainly to protect excessively long border from northern invasion.

• Many believed it is the only human work can be seen from the moon. It hasn’t been proved yet. Later American Astronaut William Pogue proved said that "it wasn't visible to the unaided eye (from space)."