How long is China's Great Wall according to the most comprehensive official survey?

China’s Great Wall measures 21,196 kilometres according to the most comprehensive official survey.

That figure, announced by China’s State Administration of Cultural Heritage in 2009, combines walls, trenches, natural barriers and multiple branches built across different periods. It is therefore much larger than the length of the most famous continuous Ming-era sections, which are commonly estimated at about 8,850 kilometres.

The Great Wall is not one uninterrupted structure built at one time. Early defensive walls appeared during the Warring States period, while the Qin dynasty connected some earlier fortifications after unifying China in the third century BCE. The Ming dynasty later constructed or rebuilt the best-preserved brick and stone sections.

A common misconception says the wall is visible from the Moon with the naked eye. This is not true; its narrow, earth-coloured structures are difficult to distinguish from orbit without optical aid. The wall’s main historical purpose was border defence, surveillance and communication rather than an impenetrable barrier.