Was it Heaven? Or Hell?

I ran accross this short story by Mark Twain who famously said “Religion is believing in what you know aint so” (I think). He was a freethinker, that’s the point I was trying to make. Nevertheless, this story I liked a lot, but I couldn’t quite figure out the ending. Whas it Heaven? Or Hell? I was never good with literature and stuff. Anyone has an opinion on this?