Great Wall of China
A fortified wall commenced under the Zhou dynasty to protect China against nomads from the north and serve as a means of communication. Various sections were built and connected until, during the Ming dynasty, 1368-1644, it extended for 1,500 miles (2,415 km), from southern Kansu province to the coast east of Peking. Rebuilt and refaced repeatedly, it is the only human-made construction visible from outer space. Photo of the Great Wall of China from Wikipedia. (Ching, 1995)