Anything that has a structure you can build in, or a tunnel to go through, or a cave with good vertical clearance.
The best ones that come to mind are keyhole, one of the 6-7 spots near the den, one of the several spots in southern aqueduct, the crevice, the arena, watcher in the jungle, the two towers near dagon dungeon entrance, and many, many more that aren’t near a POI.