Board Thread:Wiki-Related Discussion/@comment-25762747-20150310060211/@comment-25762747-20150405072259

Perhaps the Hat can travel to any world (magical or not) if the world lies within the same Universe. currently, all the worlds are from the same Universe, except the Land Without Magic. Rumple said it can only access worlds with magic, but it's uncertain whether it can access worlds withou magic (except Land Without Magic) because such worlds does not exist in the show yet. Reminder : Rumple isn't the creator of the Hat, so he can't know much about it. Perhaps the creator created it for easy access for him/herself to all the worlds in their universe.

Theory : Maybe there are more than 17 doors in the hat? there could be extra corridors and floors not shown in the show yet. There could be more than just 17 Worlds in this universe.