The Great Wall
The Great Wall extends 5,660 km from east to west in north China. It took more than 2000 years to build this Great Wall, starting from 7 B.C. to 1644. It was built mainly for self defense, in parts. It grew in length during the Qin(221-206 BC), Han (206 - 220 BC) and Ming Dynasty
when it was unified into one line.