Great Wall of China, fortifications, c.1,500 mi (2,400 km) long, winding across N China from Gansu prov. to Hebei prov. on the Yellow Sea. The wall, running mostly along the southern edge of the Mongolian plain, was erected to protect China from northern nomads. It is an amalgamation of many walls built in ancient times; the first unified wall was built in the 3d cent. B.C. by the Ch'in Ch'in (chĭn), dynasty of China, which ruled from 221 B.C. to 206 B.C.
..... Click the link for more information. dynasty. Laborers were conscripted from all over China to build it, and many of them died during the project. The wall's present form dates substantially from the Ming dynasty (1368–1644). It averages 25 ft (7.6 m) in height and is 15 to 30 ft (4.6–9.1 m) thick at the base, sloping to 12 ft (3.7 m) at the top. Guard stations and watchtowers are placed at regular intervals. The eastern part of the wall is earth and stone faced with brick, but in the west it is merely an earth mound. Successive invasions of China from the north demonstrated that the Great Wall had little military utility. Since 1949 two sections N of Beijing have been reconstructed and are open to visitors.

Great Wall of China

Chinese Wanli Changcheng

Defensive wall, northern China. One of the largest building-construction projects ever carried out, it runs (with all its branches) about 4,500 mi (7,300 km) east to west from the Bo Hai (Gulf of Chihli) to a point deep in Central Asia. Large parts of the fortification date from the 7th to the 4th century BC. In the 3rd century BC the emperor Shihuangdi connected existing defensive walls into a single system fortified by watchtowers. These served both to guard the rampart and to communicate with the capital, Xianyang (near modern Xi'an) by signal—smoke by day and fire by night. Originally constructed partly of masonry and earth, it was faced with brick in its eastern portion. It was rebuilt in later times, especially in the 15th and 16th centuries. The basic wall is about 23–26 ft (7–8 m) high; at intervals towers rise above it to varying heights. It was designated a UNESCO World Heritage site in 1987.

Great Wall of China

runs for 1,400 miles along China’s north and northwest borders. [Chin. Hist.: NCE, 538]

See : Wonders, Architectural