The Great Wall is a large defensive work of walls, passes and beacon towers, running roughly along the boundary between farming and nomadic zones.
In about the seventh century BCE the state of Chu built the Square Wall, the start of permanent defences of the Great Wall kind. After this Qi, Wei, Yan, Zhao, Qin and other states built walls one after another.
After Qin unified the realm, Meng Tian drove north against the Xiongnu and joined the old walls of Yan, Zhao and Qin, forming a continuous line of defence along the northern frontier.
The Ming rebuilt the wall on a large scale in brick and stone. Most of the wall that can be seen today is the Ming wall.
The Great Wall is the class in the chapter on Infrastructure on the defences of the Great Wall: walls, passes and beacon towers running roughly along the boundary between farming and nomadic zones. The states of the Spring and Autumn and Warring States periods built walls one after another, the Qin joined the old walls together, and most of what stands today is the Ming wall of brick and stone.
