The Great Wall of China is visible from space with the naked eye.
A common piece of trivia holds that the Great Wall of China is the only human-made structure visible from space without aid.
The evidence
The Great Wall is long but very narrow — typically only 4.5 to 9 meters wide. From low Earth orbit (around 400 km up), distinguishing it from surrounding terrain with the unaided eye is essentially impossible.
Astronauts including Chris Hadfield and Leroy Chiao have stated that they could not see the wall from the International Space Station without optical aid. NASA itself has called the claim an urban myth.
The persistence of the myth predates spaceflight — a version appears in a 1932 Ripley's Believe It or Not!, decades before any human had been to orbit.
Sources
- China's Wall Less Great in View from Space — NASA
“The Great Wall of China, frequently billed as the only human-made object visible from space, generally isn't, at least to the unaided eye in low Earth orbit.”