Highly recommend checking out one or more of those. I don't have personal experience with them, but coal mines are generally a pretty neat thing to see.
~Jade Falcon [mail][blog][page] "When people are presented with a choice between hate and love, they will choose hate. When choosing between bigotry and tolerance, they will choose bigotry. And when they are presented with the easiest of all, good or evil, bet on evil. Because it's easy." ~ me