Shinto Shrine, Shrine, Palace
It may just be a roof over a bathtub, but this here is actually a Shinto shrine.
It is indeed just a roof over a bathtub, but I guess spirits inhabit everything according to Shintoism, so there's no reason this bathtub can't be a Shinto shrine too.
きゅう, ぐう
みや
None
What god does this Shinto shrine hold? You see that "It's a-me-ya (みや)! (Mario!)"
It makes sense, the person who says "It's-a-me! (Mario)" is someone who works on bathtubs (and plumbing).