The Great Wall of China is visible from space

What actually happened

The claim predates spaceflight entirely, which is the tell. It appears in print in 1932 in a Ripley's Believe It or Not panel and in Richard Halliburton's 1938 book, decades before anyone could check.

The geometry defeats it. The wall is at most about 9 meters wide and is made of materials that match the surrounding terrain, so it has almost no contrast. Seeing it from orbit is roughly like spotting a human hair from three kilometers away. From the Moon, 384,000 km out, the entire Earth is a marble and continents are barely resolvable. Yang Liwei, China's first astronaut, said plainly after his 2003 flight that he could not see it, a statement that carried enormous weight in China and led to textbooks there being revised. Under ideal conditions with a camera and a low sun angle casting long shadows, sections have been photographed from the ISS. Plenty of other human structures, including airports, cities at night, and greenhouse complexes, are far easier to see.