Series of fortifications built across the historical northern borders of ancient Chinese states, stretching over 21,000 km. Inscribed 1987. Among the largest construction projects ever undertaken.
From Wikipedia
The Great Wall of China is a series of fortifications in China. They were built across the historical northern borders of ancient Chinese states and Imperial China as protection against various nomadic groups from the Eurasian Steppe. The first walls date to the 7th century BC; these were joined together in the Qin dynasty. Successive dynasties expanded the wall system; the best-known sections were built by the Ming dynasty (1368–1644).