Lascaux
This is cool!  Take a virtual tour of the Cave of Lascaux! 

In the 1940's a group of teens discovered this cave by accident, and came across some of the best prehistoric paintings ever found.  The cave became a huge tourist attraction, but by 1963 the increased carbon dioxide levels from all those visitors was causing too much damage to the paintings. The cave was closed to the public, and now the only way to see the paintings is to be among the chosen few who are permitted entrance.  Of course there's Lascaux II, an exact replica of the original site, or you can just click here.