Just outside of Flagstaff, Arizona, one can explore a cave that was created by lava. Super cool...and super dark!! We didn't get very far because our headlamps weren't bright enough. The tube runs for nearly a mile and was formed about 700,000 years ago.
@onewing thanx, but not really. More than anything, I've been having a stupid back problem that I can't seem to beat. I just today asked my boss if I could take an entire month off so I could properly heal. Needless to say, I'm going into work this weekend....agh.
Hope you are feeling better now.