1. Newly mapped parts of the Great Wall of China add about 180 miles to the previously believed length of the wall. Keep clicking to see what else you didn't know about the Great Wall.
2. At its peak, the wall was guarded by 1 million men. It was built to keep out Mongols and other invaders, and guard stations and watchtowers were placed at regular intervals along the wall.
3. It spans about 3,900 miles through the northern part of the country.
4. It's been estimated that between 2 and 3 million Chinese died while building the wall over centuries.
5. The first set of walls was built during the Qin Dynasty, 221 to 206 B.C. Major construction of the walls took place during the Ming Dynasty, 1388 to 1644.
6. According to urban legend, the wall is the only man-made object that can been seen from the moon with the naked eye. But that's just a myth. Like many other objects, it is sometimes visible from low earth orbit.
7. It averages 25 feet in height and 15 to 30 feet in width at its base.
8. Bricks, earth, stones, wood, tiles and lime are some of the materials used to build the wall. Some parts of it have been reconstructed.
9. On a section of the wall near Badaling almost every brick has been carved with names or other graffiti, according to Chinese state media.
10. Some parts of the wall have been demolished to make way for roads or other construction projects.
