Perhaps strange but Higurashi When They Cry. It gives me the same deeply relaxing feeling I get from when I watch Twin Peaks or watch Silent Hill or play any of the Silent Hill games. Lain gives me that same feeling, and is also a go-to comfort anime to me.

Its weird but these desolate mostly empty liminal, haunted places give me a very relaxing feeling almost like coming home. I experience the same feeling playing games like Hellmart and L.A. Noire. I don't know why that is. I'd love to know, but I don't know why myself.