I also thought it might be nice to see them without worrying about the encumbrance of footwear.  For a barefoot hiker, exploring a cave while in constant touch with its richness of textures and constant temperature of fifty-something degrees underground could only add to the depth of the experience, so to speak.  Because these places are managed "attractions" rather than simply some area of nature people walk around in, I wasn't sure what the prevailing attitude might be and thus thought it best to clarify the shoeless aspect in advance by reaching out to a couple of them. 

But the management at many of the sites seemed to strongly disagree about it, insisting that shoes were necessary, but without offering any coherent reasoning beyond "it's our policy".  Sure, it's not a question they get every day, but several of them still wouldn't budge at all when I pointed out that I go out and happily hike woods and mountains without shoes and there's nobody out there trying to declare "policy" about it.  Most of the cavern tour paths are built up level and *paved* or made of fine crushed stone anyway, to make it easier walking for typical visitors -- perhaps leaving less opportunity to step across the natural rock, but making the going no more tricky than on city sidewalks and steps.  My efforts to assure various tour directors that there would be *no* conceivable safety risk to myself or their facilities, quite the opposite in fact, fell disappointingly on some deaf ears.  Their minds were made up; they didn't want to be confused with the facts. 

Since Skyline had been the primary place I had in mind on a particular trip, I decided to go visit anyway and pull a little hack in the process.  I "made nice" and went in with the flats on, and simply pocketed them about halfway through the tour and felt *so* much better thereafter.  It was early morning off-season and the tour group consisted of exactly myself and the guide, and we'd already had a good conversation about "real caving" and the NSS and the groups that would come in over the summer to map even more of the unexplored sections.  So we were already on a pretty friendly basis, and he completely understood why I was now *safer* on the occasional steeper path inclines that we had both been slipping on, and didn't actively object to my decision at the time.  We finished the tour normally, and then I then "served some paperwork" to the available management on the way out, handing off a copy of my slightly reworded version of Bob Neinast's multi-point document.  The general manager I'd spoken to wasn't around that morning, so I couldn't finish our otherwise nonproductive phone conversation from before, but at least I made the effort for those few who were present and Skyline *is* a pretty interesting place to see in its own right anyway.

After I got back home from that trip I decided to proactively research more of this field, and found a nice article listing just about all the I-81 corridor underground attractions.  [Note its date; entrance fees are significantly more nowadays.]  Here I've listed the major sites in the same red/green/maybe color format as the main page, and roughly in order while going south on I-81 except that some require getting fairly far off the highway.  Status as of this writing was determined mostly by phone calls, and going forward may vary depending on who you talk to, but if there's any question it's certainly worth convincing any doubters on a given staff to get over it already and acknowledge that subterranean barefootin' is completely okay.

Some of the other people I first spoke with at Natural Bridge made the odd distinction that while walking the outdoor nature trails sans shoes would be fine, there was some perceived difference with regard to entering the cave.  That one I *don't* understand at all, but such an attitude is common and they are probably basing it on some erroneous concept of greater liability once a visitor is "inside" some space.  Witness the similar distinction with regard to inside a store versus walking across its parking lot -- again, as soon as the threshold to "indoors" is crossed, suddenly the prejudice kicks in.  It's a very odd response.

Another potential counterargument about caves could arise concerning skin oils, which is one reason visitors are asked to not touch any formations or even the cavern walls.  An accumulation of organic oils that would never be present in nature can change a rock surface in a way that affects water flow; Skyline has one particular piece of upended stalactite [placed by humans after being found detached on the floor many years ago] that they allow guests to rub "for good luck", and it has a distinctive surface sheen that's different from everything else.  However, healthy dry bare feet are unlikely to emit much in the way of such effluents in the process of walking, and certainly not in a way that could leap off an artificial walking path onto something else.  The cave floors and paths get plenty of crap from outside on peoples' shoes and clothing anyway, one of the concerns noted in preventing spread of white-nose fungus to resident bats, but think about it: shoes with a tread are going to harbor far more detritus from prior places than a bare foot ever could.  A barefooter can readily feel when something is stuck to a sole and brush it off before it can travel very far.

Tour guides deliver a continual stream of warning to their visitors, about slippery conditions ahead and to watch their heads through low passages.  In other words, they're doing their "duty of care" the whole way through, and if someone does suffer a bump to the head or the butt it is certainly not the facility's legal responsibility.  Guided or not, people who go to tour caves should know what they're getting into and will certainly shoulder the entire burden of risk in the process.  As in many other situations, being barefoot allows me to feel *exactly* how slippery conditions are underfoot and adjust my stride, so it's yet another situation where shoes and "safety" are quite unrelated and perhaps even at odds.

It's unfortunate that in a supposedly so enlightened modern society that anyone needs to make this much effort to stand up for one's own rights, against the simple fact that so many people are uninformed.  There's always this newfangled Internet-thang that can help, but they need to get curious enough to pursue the truth.