Utter Inn - Stockholm, Sweden
When you first see Sweden's Utter Inn (that's "Otter Inn" in English), you may not be impressed. It looks more like a floating outhouse than a private island, which is how the inn is advertised. But looks can be deceiving, and no matter what your first impressions are, your stay will be memorable.
Climb down the ladder to the lower floor, and you're in an underwater hotel room, complete with large windows, twin beds and a table. There's no room service (though a boat will deliver dinner for an additional fee), no concierge and no communication with the outside world. It's just you, the fish and an inflatable canoe that you can row over to a nearby uninhabited island for a change of scenery if you like. It's peaceful, sometimes frightening and like no other hotel on earth.