China is home to the Great Wall, the vast defensive network in East Asia.
The Great Wall is not one continuous wall built at one time. It is a connected system of walls, trenches, passes, fortifications, and watchtowers constructed and rebuilt by several Chinese states and dynasties. Its total measured length, including branches and associated structures, is more than 21,000 kilometres.
The Ming dynasty built or substantially rebuilt many of the best-preserved sections visible today, especially from the fourteenth to seventeenth centuries. These sections commonly used brick and stone, while earlier walls often relied on packed earth and other local materials. The defenses helped control movement, protect agricultural regions, and regulate trade routes.
The popular claim that the Great Wall is visible from the Moon without aid is false. Its width and colour make it difficult to distinguish from the surrounding landscape even from low Earth orbit.