The Great Wall of China is a collective of several walls built between 5th century BC to 221 BC between the borders of the states of Qin, Oi, Wei, Yan, Zhao and Zhongshan. After Qin Shi Huang won all the opposing states and unified China in 221 BC, in order to barricade his entire empire he ordered to destruct some sections of wall that were dividing his empire and built a new wall connecting to the remains of former walls.