THE GREAT WALL Of CHINA

The great wall of China is the longest structure ever built. Its

length is about 4,000 miles ( 6,400 kilometers ), and it was erected

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 sight of the great wall. Most of what is

now called the Great Wall dates from the Ming dynasty

(1368-1644 ). The eastern end of the surviving Ming wall is at

Shahaiguan, a town near Qinhuangdao on the coast of the BoGulf.

In the west, the wall ends near the wall reached as far east as

Dandong and as far west as Dunhuang, near Anxi. 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 2,150 miles (3,460 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. 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 once. 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 gover4nment 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.