China is home to the Great Wall, the world’s longest defensive wall system.
The Great Wall is not one continuous structure built at one time. It is a network of walls, trenches, passes, watchtowers, and fortifications constructed and rebuilt by successive Chinese states over more than two millennia.
The best-preserved sections date mainly from the Ming dynasty, which ruled from 1368 to 1644. These walls protected approaches to agricultural regions and served as military communications and border-control infrastructure.
A widely cited Chinese survey measured all sections at about 21,196 kilometres, including natural barriers and multiple branches. The wall is not reliably visible from the Moon with the unaided eye, a popular myth repeated about it.