The Great Wall 长城

The Great Wall, Chang Chen in Chinese, means Long Wall literally. The history of the Wall can be traced back 656 B.C. during the reign of King Cheng of the States of Chu. Then when the first emperor of Qin unified China after he conquered other states, he ordered to connect all these individual Walls from East to West. Afterwards During there were many dynasties that rebuilt or repaired the Wall to against the emery from Northern China. Particularly Han and Ming Dynasty constructed much longer Wall than other periods. The longest Wall in the history was bull during Han Dynasty which extends about 10,000 km from modern East Liaoning Province to Lop Nor near the Taklimakan Desert against the nomad invaders Huns, and the ruin of the Great Wall of Han Dynasty still can be seen in Gansu, Shanxi, Xinjiang provinces. Mostly the Wall that the visitors can view was built in Ming Dynasty (1368—1644 A.D) that was built with stable bricks and rocks, extending about 7000 km from Shanhai Pass in the eastern Liaoning Province to Jiayu Pass in the Hexi Corridor of Gansu Province.
There are several sections of the UNESCO World Heritage Site Great Wall of China, most notably Badaling, Jinshanling, Simatai and Mutianyu. When you travel to China, the Great Wall is a must-see.

Here is the information about the Great Wall during different periods.
Qin Dynasty (221 B.C- 207 B.C)
Length 7,000 km
From Eastern Liaonin Province to Lintao, Gansu Province

Han Dynasty （202 B.C—8 A.D，25 A.D—220 A.D）
Length 10,000 km
From Eastern Liaonin Province to Lop Nor near the Taklimakan Desert

Ming Dynasty (1368-1644 A.D)
Length 7,000 km
From Shanhai Pass, eastern Liaoning Province to Jiayu Pass in the Hexi Corridor of Gansu Province