Great Wall

Great Wall, the only man-made structure that is visible from outer space, is the eighth wonder in the world. Construction of the Great Wall started in the 7th century BC. The vassal states in the northern parts of the country each built their own walls for defense purposes. When Qin unified China in 221 BC, it joined the walls to hold off the invaders from the north and extended them to more than 5,000 kilometers. The Great Wall was renovated several times after the Qin Dynasty. The one we see today was the result of a major renovation in the Ming Dynasty. With a total length of 6,700 kilometers, it extends from Shanhai Pass in the East to Jiayu Pass in the West. What lies north of Beijing is but a small section of it.