Kartchner Caverns in Arizona

If you're in Arizona anytime in the near future and looking to do a little spelunking you might want to check out the Kartchner Caverns (about 45 minutes southeast of Tucson).  The Caverns were discovered just over thirty years ago when two college students caught a whiff of the sweet smell of bat droppings near a sinkhole and decided to explore.  In all, over two-miles of trails were found and some of the rooms have ceilings up to a hundred feet high.  For more info check out this great article from the Seattle Times.