Here’s the quickest and dirtiest ways to make simple caves for games.
There are limitations, but the speed it quite impressive.
This covers two ways. The first is meatballs, and the second is the skin modifier (with some smoothing). You probably don’t need to watch the video now I’ve said that.
Hope this helps someone.
Even though I probably won’t be making a cave anytime soon, this puts modeling method ideas into my head.