Caves Branch Adventure Company has some great pictures from their excursion through 7 miles of the underground. When was the last time you went cave tubing?

"You will enter and exciting world of rivers that disappears into the underworld as you float in the darkness where only your headlamp and those of your fellow adventurers will light the way. It sounds scary but it is not! It is exciting and fun - lots of screaming and echoes too! Whenever you look around you will realize that you are swirling around stalagmites jutting from the river and stalactites looming from above. There are also underground waterfalls and a crystal cathedral. This is a spiritual center to the ancient Maya."