What is the longest man-made structure in the world, according to the measured length of the Great Wall of China?

The Great Wall of China is the world’s longest man-made structure, with surveyed remains measuring about 21,196 kilometres in total.

The name refers to a network of walls, fortifications, trenches and natural barriers built or connected across northern China over many centuries. Several early states constructed defensive walls, while the Qin dynasty linked some earlier sections after unifying China in the third century BCE.

The best-preserved sections are largely associated with the Ming dynasty, which ruled from 1368 to 1644. These later walls used brick and stone extensively and included watchtowers, gates and signal systems designed to monitor movement and communicate warnings.

The Great Wall is often described as visible from the Moon, but that claim is a myth: it is generally too narrow to see unaided from lunar distance. The measured total includes many separate branches, so it is not one continuous wall.