Great Wall (Civ4)/Civilopedia

The Great Wall of China is one of the largest and most famous man-made constructions in the entire world. Chinese rulers built the Great Wall to ward off attack from nomadic tribesmen living in modern Manchuria and Mongolia. Interestingly, the Great Wall was not designed to keep the nomads out - the Chinese knew it was all but impossible to defend such a long border - it was designed to make it difficult for the raiders to carry off loot, thus making raids far less profitable and thus less worth the risks involved.
There have actually been five different "Great Walls" built by different Chinese dynasties. The first four were constructed of earth and have since all but disappeared. The current wall was built almost entirely by the Ming Dynasty between 1368 and 1640 AD. This wall was constructed on a grander scale, using more permanent materials (like stone). The Ming wall stretches for 3,948 miles from Shanhai Pass on the Bohai Gulf in the east to Lop Nur in the southeast portion of Xinjiang's Uygur Autonomous Region in the west. This was the region where the Silk Road first entered China, and a series of watchtowers which could communicate via smoke signals were intended to pass messages rapidly along the vast length.
In pure military terms, the Great Wall turned out to be something of a failure. The Manchus were able to bribe a Chinese general to let them pass through the wall, so it turned out to be of little value in stopping a major barbarian attack. After the Manchus conquered China, the borders of the country extended far to the north, rendering the wall irrelevant. The sheer cost of the wall was also staggering, and the cost in human lives is said to have exceeded over one million souls (the Great Wall is sometimes nicknamed "the long graveyard").
Today much of the Great Wall is in a state of disrepair - though the tourist regions are well-preserved, much of the rest of the structure is crumbling, and perhaps only 20% of the wall is in good condition. Despite its decay, the Great Wall remains one of China's most popular tourist attractions and a true wonder of the world.