The Great Wall of China is an ancient Chinese fortification built from the end of the 14th century until the beginning of the 17th century, during the Ming Dynasty, in order to protect China from raids by the Mongols and Turkic tribes. In Chinese the wall is called "Wan-Li Chang Cheng" which means 10,000-Li Long Wall (10,000 Li = about 5,000 km).
The Great Wall started as earth works thrown up for protection by different States. The individual sections were not connected until the Qin dynasty (221-206 B.C.). Qin Shihuangdi, First Emperor of Qin began conscripting peasants, enemies, and anyone else who wasn't tied to the land to go to work on the wall. He garrisoned armies at the Wall to stand guard over the workers as well as to defend the northern boundaries. The tradition lasted for centuries. Each dynasty added to the height, breadth, length, and elaborated the design mostly through forced labor. The Wall in Qin Dynasty was located much further north than the current Great Wall, and very little remains of it.
The Great Wall that can still be seen today was built during the Ming Dynasty, on a much larger scale and with longer lasting materials (solid stone used for the sides and the top of the Wall) than any wall that had been built before. The watch towers were redesigned and modern canon were mounted in strategic areas. The Portuguese had found a ready market for guns and canon in China, one of the few items of trade that China didn't already have in abundance.
The Ming Dynasty Great Wall starts on the eastern end at Shan Hai Pass, near Qinhuangdao, in Hebei Province, next to Bohai Gulf. Spanning nine provinces and 100 counties, the final 500 kilometers have all but turned to rubble, and today it ends on the western end at the historic site of Jiayu Pass, located in northwest Gansu Province at the limit of the Gobi Desert and the oases of the Silk Road. Jiayu Pass was intended to greet travelers along the Silk Road. Even though The Great Wall ends at Jiayu Pass, there are many watchtowers extending beyond Jiayu Pass along the Silk Road. These towers communicated by smoke to signal invasion.
The primary purpose of the wall was not to keep out people, who could scale the wall, but to insure that semi-nomadic people on the outside of the wall could not cross with their horses or return easily with steal property.
The government ordered people to work on the wall, and workers were under perpetual danger of being attacked by brigands. Because many people died while building the wall, it has obtained the gruesome title, "longest cemetery on Earth" or "the long graveyard". Their bodies were not entombed in the wall, however. A body buried in the wall would have weakened its structure, so workers were buried nearby instead.
While some portions near tourist centers have been preserved and even reconstructed, in most locations the Wall is in disrepair, serving as a playground for some villages and a source of stones to rebuild houses and roads. Sections of the Wall are also prone to graffiti. Parts have been bulldozed because the Wall is in the way of construction projects.
The materials used are those available near the site of construction. Near Beijing the wall is constructed from quarried limestone blocks. In other locations it may be quarried granite or fired brick. Where such materials are used, two finished walls are erected with earth and rubble fill placed in between with a final paving to form a single unit. In some areas the blocks were cemented with a mixture of glutinous rice and egg white. In the extreme western desert locations, where good materials are scarce, the wall was constructed from dirt rammed between rough wood tied together with woven mats.
The Great Wall is one of the largest building construction projects ever completed. It stretches across the mountains of northern China, winding north and northwest of Beijing. It is constructed of masonry, rocks and packed-earth. It was over 5,000 km (=10,000 Li) long. Its thickness ranged from about 4.5 to 9 meters (15 to 30 feet) and was up to 7.5 meters (25 feet) tall. The Wall is included in lists of the "Seven Medieval Wonders of the World" but was of course not one of the classical Seven Wonders of the World recognized by the ancient Greeks. The Wall was made a UNESCO World Heritage Site in 1987.
The wall is complemented by defensive fighting stations, to which wall defenders may retreat if overwhelmed. Each tower has unique and restricted stairways and entries to confuse attackers. Barracks and administrative centers are located at larger intervals. In addition to the usual military weapons of the period, specialized wall defense weapons were used. Reproductions of weapons are displayed at the wall.
Over the past few centuries, the Great Wall has served as a source of building materials for local farms and villages. Aerial photos show that in sections, only the top battlements show -- the center of the wall has filled with sand and silt. The same brutal isolated conditions which made the Great Wall a triumph of engineering and determined planning make restoration problematic and slow.