The Great Wall, "Wan-Li Ch'ang-Ch'eng" (10,000 Li Long Wall), is one of the largest building construction projects ever carried out. It streaches approximately 4,000 miles (6,400 km) west to east from the Jiayu Pass (in Gansu Province) to Po Hai at the mouth of the Yalu River (in Liaoning Province), and is supposedly clearly visible from the moon. Construction of The Great Wall started in the 7th century B.C.The vassal states (under the Chou Dynasty) in the northern parts of the country, each built their own walls for defensive purposes.

The Great Wall stands 25 feet high on average. Its base measures between 15-30 feet thick. It is the only man-made structure that can be seen from space. Millions of people come to travel along the wall each year. Since parts of the wall are falling apart, the Chinese government has been repairing parts of it since 1949.

The majority of the Great Wall was built in 221-204bc, but construction first began in about 400bc. The purpose of the wall was to defend against nearby Mongolian tribes. It was completed during the Sui dynasty, which was between 581 and 618ad. Much of the Wall fell down during this time, but was repaired during the Ming dynasty (1368-1644ad).

After many conflicts, China was united in 221 B.C. In 214 B.C. Shih Huang-Ti (the first Emperor of a united China) connected a number of the existing defensive walls into a cohesive unit fortified by a system of watchtowers. These served both to guard the rampart against attack as well as to communicate with the then capital, Hsien-Yang (near Sian), by signal (smoke by day; fire at night). The principal enemy against whom the Great Wall was built were the Hsiung-Nu (the nomadic tribes of the northern steppes). The wall at this time extended more than 10,000 li or 5,000 kilometers which is the origin of the name of the 10,000-li Great Wall. An interesting story is that Emperor Shih Huang Ti would not let people that died working on the wall have a proper burial. Instead, they were to be built into the wall to save time. Since this, archeologists have found tombs built into the Great Wall.

The Great Wall was originally constructed partly of masonry and partly of earth and was faced with brick in its eastern portion. It was substantially rebuilt in later times. A major renovation started with the founding of the Ming Dynasty in 1368, and took 200 years to complete. The wall we see today is almost exactly the result of that effort.