Great Wall of China

The Great Wall of China is a series of stone and earthen fortifications in northern China, built originally to protect the northern borders of the Chinese Empire against intrusions by various nomadic groups. Several walls have been built since the 5th century BC that are referred to collectively as the Great Wall, which has been rebuilt and maintained from the 5th century BC through the 16th century. One of the most famous is the wall built between 220–206 BC by the first Emperor of China, Qin Shi Huang. Little of that wall remains; the majority of the existing wall was built during the Ming Dynasty (1368-1644).

The Great Wall of China, one of the greatest wonders of the world, was listed as a World Heritage by UNESCO in 1987. Just like a gigantic dragon, the Great Wall winds up and down across deserts, grasslands, mountains and plateaus, stretching from Shanhaiguan in the east, to Lop Nur in the west, along an arc that roughly delineates the southern edge of Inner Mongolia. The most comprehensive archaeological survey, using advanced technologies, has concluded that the entire Great Wall, with all of its branches, stretches for 8,851.8 km (5,500.3 mi). This is made up of 6,259.6 km (3,889.5 mi) sections of actual wall, 359.7 km (223.5 mi) of trenches and 2,232.5 km (1,387.2 mi) of natural defensive barriers such as hills and rivers.

Before the use of bricks, the Great Wall was mainly built from rammed earth, stones, and wood. During the Ming Dynasty, however, bricks were heavily used in many areas of the wall, as were materials such as tiles, lime, and stone.

It has become a space-based myth. The Great Wall of China frequently billed as the only man-made object visible from space. It certainly isn't visible from the Moon.