From the maps there seems to be quite a few, in Europe too. Though even just a handful of caves seems like a lot to me.

Caves are a lot like any building structure; many have enormous interiors in certain parts while others are like you describe. In fact caves are typically more open than regular buildings. Many of us, in fact the three of us on our end, aren't that athletic either.

I may have to recommend that to the friends. There's a cave near us like that, it looks highly unassuming but it's so large that, had it not filled up with water following a mishandling during mining, it would count as the world's largest natural bombshelter.

I wasn't there when it happened, but one friend found a new subspecies and the other found small traces of cave art, not profound enough for a consensus to confirm anything was going on but profound enough that a layperson would have no doubt. I haven't found many exciting things, except maybe remnants of people seeking refuge. I haven't been hands-on in the majority of cave exploring, but I have some memorable moments saved in the form of photos (here's hoping Lemmy fixes photos soon).

If you're wearing the right equipment, it's mostly a matter of watching one's step and knowing small bits of advice (for example, never light a match in a cave, ever). It should be remembered people mine in caves for a living. The two friends aren't even that athletic, usually going off in different directions depending on their skills (one of them I've never seen so much as climb a hill).

Worked in caves for 3+ years now. In my neck of the woods the worst ya gotta worry about is rabies, but the bats here seldom bite unless provoked. We're more of a threat to the bats though since we can spread white nose syndrome which can wipe out bat colonies.

Some very important notes for your son:

Caves are cold so not many insects go down there.
If he got bit by a tick check for tick diseases. I know the big one around here is Lyme Disease. If he has a bullseye shape around the bite that’s a sign of an infection. I don’t know if other tick diseases are prevalent in your area.

If he was in close contact with bats and may have been bitten get him checked for rabies. While very rare, there are still occasional cases across the US. It can remain dormant for a very long time but once it crosses the blood brain barrier and infects the brain there is no help. It’s better to get him checked and vaccinated early than wait and see.

Just some numbers on the rabies, there are about 5k animal cases reported yearly nationwide, mostly wild animals. Only 1-3 yearly reports in humans. So it’s rare and unlikely, but it’s just not something you fuck around with and risk.

Even though a bat or other animal could always carry them in from outside, they're far less common in the actual caves.

I looked that up just now and already I see the first red flag on the game cover. Torches are advised against in caves because the fire can heat up surrounding rocks which can cause a pressure buildup.