7.The Great Wall

From the 7th century B.C. through to the 17th century, the Chinese spent more than 2,000 years building the Great Wall, which stretched about 200,000 kilometers in total. However, most parts of the Great Wall have disappeared, except for the Ming Dynasty Great Wall. As one of the seven wonders of the medieval world and the only human artifact visible from out space, it was listed as World Heritage by UNESCO in 1987. Winding up and down across deserts, grasslands, mountains and plateaus, the Ming Dynasty Great Wall measures only 8,851.8 kilometers now, from east to west, and has been destroyed by erosion and human development in the surrounding regions. The Great Wall has been included on the list of 100 endangered sites by the World Monuments Fund.