For instance, a moon shaped room with the entrance on the left side, floating to the left of the Great Hole to Ix, as seen when you get to the top of the Groddle Ladder. The moon would be placed in the upper left corner of the screen of the Great Hole to Ix. I think you'd need levitation to get there; might be too high for spinach.
Something similar could be placed in The Drop at Ilminskie. A cavern room of some sort.
Dunno any other great locations for this sort of thing, but it would make levitation a bit more excellent if there were places only accessible via levitation.