Check out this breathtaking crystal cave found inside of a huge marble mine

It's hard to imagine that these sorts of enormous, human-made mines, this one with 60' ceilings, exist all over the world. It's equally hard to believe that extensive cave systems, this one filled with many different types of crystal formations, also exist beneath our feet.

Now imagine finding one inside of the other. These caving "duuuuuudes" who explored it couldn't believe their luck. Duuuuude!