Have you ever wondered, what would be the first thing you will see when nearing the planet, coming from outer space? In fact, there are only two man-made structures visible from space: The Pyramids of Giza and the Hoover Dam. It is a general (but wrong) belief that The Great Wall of China is visible from outer space. Despite its great length, the wall is too thin to be noticed from such an enormous distance. NASA claims that it is barely visible from a low Earth orbit, and only under nearly perfect conditions.