You've probably seen this "fact" a bunch of times (we here at OMG Facts certainly have):
"The Great Wall of China is the only human-made object that can be seen from outer-space."
Turns out it's not even true. The first known publishing of this "fact" was back in 1938, long before anyone was traveling in space. Since then lots of people have gone into outer space and looked at the Earth and haven't found the Great Wall.
The Great Wall is huge (5500 miles long) but in order to be visible from far away it would also have to be very wide and distinct looking from the ground. The Great Wall is very thin. If it were visible from space, every interstate highway would be too!
On the other hand, you can see the Pyramids of Giza from space. You can also see Minutemaid Park, the Toyota Center, and the George R. Brown Convention Center in Houston, TX
(source 1, 2, 3)