Photograph of the Great Wall of China
First built between 220–206 BC by the first Emperor of China, Qin Shi Huang, the great walls main construction was during the Ming Dynasty. Stretching across China for over 8,851.8 km ( or 5,500.3 miles) the Great Wall was used as defensive tool.
A popular myth is that the great wall is visible from the moon, it is not. From low orbit it is, barely visible, as are many other man made objects.