I don’t remember where I saw it, but I watched a video about different exo-planets. One that stuck out to me was a planet that had miles of ice but possibly also a liquid water ocean underneath. If intelligent life evolved down there, they would probably have no clue about the wider universe and think their world is all that exists. Imagine such a being’s reaction if they ever drilled up through the ice. I feel like this could be turned into a good sci-fi book.