The claim
“The Great Wall of China is visible from space with the naked eye”
Disputed
Not the way the legend says. It's too narrow and blends into the land, and astronauts disagree about whether they've seen it.
What's really going on
The claim is often repeated as settled fact. Wikipedia sums up the claim's accuracy as "questionable". The Wall is long but narrow and built from local materials, so it blends in. Some astronauts say they have seen it, while China's first astronaut said he could not.
The receipts
“Various factoids in popular culture claim that the Great Wall can be seen (with the naked eye) from space, with questionable degrees of veracity.”
“A significant barrier to that is that although the Wall is long enough, it is too narrow, and astronauts report that, as it is made of local materials, there is a camouflage effect as well.”
“Astronauts testifying to its visibility from space include Gene Cernan and Ed Lu; Yang Liwei, China's first astronaut, meanwhile stated that he had not been able to see it.”
More myths
Myth“Bulls charge because they hate the color red”Bulls are dichromatic, a kind of color blindness, so the red of the cape is irrelevant to them. Myth“Goldfish have a three-second memory”Goldfish remember things for months, not seconds. Myth“Archaeologists found edible honey in ancient Egyptian tombs”This 'fact' is all over the internet, but no edible honey has been found in Egyptian tombs.