We've been there a few times, so there's a lot we know about the Moon. However, there is also much we don't know. And some say there could be a lot that is hidden. There are many photographs, for example, taken by the lunar missions of both the U.S. and the Soviet Union, that seem to show artificial structures and artifacts.
Are there good, logical explanations for these things... or is there something happening on the Moon that most of us don't know about? Go look at this gallery and decide for yourself.