There's one in Louisville Ky. They decorate and you can drive through at Christmas time, they also have zip lines in there you can ride. There's a whole underworld here where I live, Mammoth Cave is only a few miles from me.
Mega Caverns. I've been there. I went to huge party/dance there a few years back.
I've also been to Mammoth Cave.
I used to own some property in Brandenburg KY, there is a cave system near there as well. I think they had to seal the entrance up. Somebody managed to get stuck and died.