No one has asked before, but there have been a few:

In Kentucky I worked in the Mammoth Cave area for a couple of years as an Interpretive Naturalist. I led tours through Diamond Caverns, a formation cave in the Mammoth System, and of course I visited the National Park and toured portions of the dry Mammoth Cave itself. I was also in a select group that got to tour Crystal Caverns, Floyd Collin's old cave (the one he never completely got away from - I think the "Ballad of Floyd Collins" is in the DT here).

I toured Lehman Cave in Nevada, Caverns of Sonora in Texas (near Iraan and Sonora, Texas, with fabulous formations and helectites), Carlsbad Caverns (NM/TX), Howe Cavern in upstate New York, and the very cleverly designed man-made cave at the Arizona Sonora Desert Museum. I was quite impressed at all of the features they got right in it.

As a kid I visited deserted mines (a popular activity at summer camp - old horizontal mines that are in hard rock) and numerous caves with no names while up climbing in various places - the Cascade and Olympic Mountains in Washington and the Ajo Mountains in Arizona (Organ Pipe Cactus Natl Monument), in particular.

I seem to have a fondness for caves! I haven't been spelunking, but mostly for lack of opportunity.

SRS