The Great Wall is a system of fortifications developed over successive dynasties, rather than one building completed in a single campaign.
When was it built?#
UNESCO records the joining of earlier defensive works under Qin Shi Huang around 220 BCE, with construction continuing through the Ming dynasty. Its synthesis describes a historical defensive network exceeding 20,000 kilometres. That network should not be mistaken for a single visitor route.
What does the system include?#
Walls, watchtowers, shelters, tracks, fortresses and passes formed parts of the defensive system. These different structures help explain why a single length does not describe every aspect of the heritage.
Can it be seen from the Moon?#
No. NASA explicitly rejects the Moon-visibility myth. UNESCO's older criteria text repeats that claim, so it should not be accepted merely because it appears on an official page.