@kus-knee your post reminded me of a tour of a cave I took as a child. During the tour I asked the question "Is there ever fog in a cave?" The guide didn't know, but afterwards discussed it with their local expert. They told me that they have never had that question, let alone from a child, but that there is in fact always a thin fog in caves!

They gave me a free book to keep my curiosity strong. Thanks for your post, and for the trip