Today I dug into a cave network without an exit, just lots of tunnels and no way out except the way I came. Didn't find a single cavemouth even after I mapped the entire thing.
In w3 I thought that every cave had an exit, if I could see a cave from another cave with no way in there was a way in from the surface somewhere else. I guess in this world there's caves generated without exits. Has anyone else found a place like this?