Great Wall of China

Great Wall of China is the longest structure ever built. Its total length— including branches—is about 4,500 miles (7,240 kilometers), and it was erected entirely by hand. The wall crosses northern China between the east coast and north-central China. Over the centuries, various rulers built walls to protect their northern border against invaders. Some of the walls stood on or near the site of the Great Wall. Most of what is now called the Great Wall dates from the Ming dynasty (13681644). The eastern end of the surviving Ming wall is at Shahaiguan, a town near Qinhuangdao on the coast of the Bo Gulf. In the west, the wall ends in the Lop Nur region of the Xinjiang province. But during some periods, the wall reached as far east as Dandong and as far west as Dunhuang, near Anxi. Description. Parts of the Great Wall have crumbled through the years. However, much of it remains, and some sections have been restored. The main part of the wall is about 2,500 miles (4,020 kilometers) long. Additional branches make up the rest of its length. One of the highest sections of the Great Wall, on Mount Badaling, near Beijing, rises to about 35 feet (11 meters) high. This section is about 25 feet (7.6 meters) wide at its base and nearly 20 feet (6 meters) at the top. Watchtowers stand about 100 to 200 yards (91 to 180 meters) apart along the wall. The towers, about 40 feet (12 meters) high, once served as lookout posts. In the east, the wall winds through the mountainous Mongolian Border Uplands. This part of the wall has a foundation of granite blocks. It has sides of stone or brick, and the inside of the wall is filled with earth. The top is paved with bricks set in mortar. The bricks form a road that was used by the workers who built the wall and by the soldiers who defended it. Farther west, the Great Wall runs through hilly areas and along the borders of deserts. Stone and brick were scarce in these hilly and desert areas, and so the workers used earth to build this section of the wall. They moistened the earth and pounded it to make it solid. History. Written records indicate that the Chinese built walls along their borders as early as the 600's B.C. Emperor Shi Huangdi of the Qin dynasty (221-206 B.C.) is traditionally regarded as the first ruler to conceive of, and build, a Great Wall. Most of the Qin wall was north of the present-day wall. Shi Huangdi had the wall built by connecting new walls with older ones. Building continued during later dynasties, including the Han (202 B.C.-A.D. 220) and the Sui (581-618). By the time the Ming dynasty began in 1368, much of the wall had fallen into ruin. In response to the growing threat of a Mongol invasion, the Ming government began building a major wall in the late 1400's. This wall included most of what remains today. Like earlier ones, it protected China from minor attacks but provided little defense against a major invasion. Through the centuries, much of the Great Wall again collapsed. However, the Chinese Communists have done restoration work since 1949, when they began to rule the nation. The wall no longer serves the purpose of defense, but it attracts many visitors. Tourists from around the world come to see the wall. Historians study writing and objects found in fortifications and tombs along the structure. Scientists study earthquakes by examining parts of the wall that have been affected by these earth movements.