What is the longest wall in the world, measured by its complete historical network?

The Great Wall of China is the world's longest wall when its complete historical network is measured.

A national survey reported a total length of about 21,196 kilometres, including walls, trenches, natural barriers, and sections from different historical periods. The structures were not built as one continuous project; many states and dynasties constructed or rebuilt defensive lines over more than two millennia.

The best-known surviving sections date from the Ming dynasty, which ruled from 1368 to 1644. These parts used bricks and stone extensively and protected approaches to important settlements and routes.

A common myth says the Great Wall is visible from the Moon with the naked eye. It is not. The wall is an extraordinary human construction, but its narrow width and similar colour to the landscape make it difficult to see from orbit without photographic assistance.