As a symbol of ancient Chinese civilization, The Great Wall of China has stood for more than 2,000 years. The Great wall of China was built in stages from the 5th century BC up to the 16th century AD as protection against northern nomadic tribes. Stretching from the coast of the Bohai Bay in the east and ending at the Jiayu Pass in the west, it snakes along the back of mountains, deserts and valleys for 6,350km (3900 miles). It is said to be 1 of the only 2 human engineering projects visible by astronauts from space with the naked eye. Built of huge granite slabs and special sized bricks, the Great Wall at Badaling 75km (47 miles) north of Beijing is most typical part of the Wall during the Ming dynasty (1368-1644). There the wall is wide enough for 5 horsemen to ride abreast or 10 men to walk side by side.