If you have never felt the moist, heavy air of being 800 feet underground, I highly recommend it. If you have never sat cross legged on a stone bench in the maw of a cavern and meditated until your toes tingle, I would encourage you to give it a try. If you have never felt the wrenching, disorienting feeling that comes from ripping straight out of the earth’s belly by elevator after hours of silent reverie, I assure you, the sensation is quite overwhelming.
If you have never tried to get good photography shots (sans flash) in a dim, wet room, navigating your tripod on a small path with hundreds of your fellow visitors, you are probably smarter than I. (But I loved every minute of it.)
(You can find these shots, in better detail, on Flickr)