Fish is always on the menu at the Jules Undersea Lodge in Key Largo, Florida.
Situated 21 feet beneath the sea, guests can enjoy unlimited diving and magnificent views through the 42 inch windows. While you're down there, you can earn yourself a PADI diving certificate, or take a three-hour scuba diving crash course.
Birds' eye views are guaranteed at the Perche dans Le Perche treehouse in Normandy. At 50 feet off the ground, this cosy nest sits within the boughs of an ancient chestnut tree in the beautiful Perche National park. It sleeps five and has two bedrooms, a small kitchen, shower room and wi-fi - so there's plenty of opportunity to twitter.
For more treehouses, see Ten of the best treehouse hotels.
Live like a troglodyte at the Gamirasu Cave Hotel in Cappadocia, Turkey. Located in a 1,000-year-old Byzantine monastic retreat, part of the cave was used by Christian monks until recently. Book into one of the monks' cells, or treat yourself to a deluxe room with vaulted ceilings, fireplace, locally made carpets and wi-fi. Horse riding and Turkish cookery classes will keep you amused.
You don't have to be barking mad to stay at Dog Bark Park Inn in Cottonwood, Idaho... but if you are, it helps. Guests entering the 12-foot tall beagle will find a world of canine wood carvings and dog-shaped cookies on their pillow. There's a bedroom in the dog's head and a cosy alcove in the muzzle and lots of glorious countryside all around for walkies.
No, you are not dreaming! Slanted floors, suspended beds and mirrored rooms are some of the surreal surroundings created by artist Lars Stroschen at the City Lodge Propeller Island, Berlin, Germany. Check into a slanted room which makes grandma's bed seem to fly; sleep in a coffin, a prison cell or on a bed suspended from the rafters; catch your reflection in the diamond-shaped mirrored room or sleep beneath the floorboards. This one defo wins our prize for the weirdest hotel we could find.
This vintage Boeing 727 fuselage at the Costa Verde Hotel, Costa Rica, is just the ticket for high flyers. Perched on a 50 foot pedestal in the Manuel Antonio National Park, the two-bedroom suite comes with teak panelling, hand-carved furniture, two bathrooms, air-conditioning, kitchenette and balcony. Will this idea take off? Watch this space...
A night in this tiny Calvados cask in Normandy is guaranteed to be a barrel of laughs. Once used to store 10,000 litres of Calvados, the barrel on the Domaine de La Corp au Grip estate has been transformed into a circular bedroom which is ideal for two people. The owner runs cookery workshops too.
Once used by the US military to house radar defending the Panama Canal, the unusual Canopy Tower in Soberania National Park, Panama, is now an eco lodge. The bedrooms are at tree-top level and the observation deck and restaurant have panoramic windows that provide amazing views of the forest canopy and more than 500 species of birds.
You won't throw money down the drain at Das Parkhotel, Austria - you'll be living in it. These giant concrete drain pipes have a double bed, storage, light and power but despite all the piping, there's no toilet or shower - public facilities are nearby. Guests pay according to how much they can afford. The drainpipe idea has proved so popular that five more drain pipes will soon open near Essen, Germany.
Staying 155 metres underground will not guarantee a good night's sleep but at least you won't need black-out blinds. Guests staying at this one-room hotel in the Sala Silvermine, Vastmanland, Sweden, are provided with a delicious candle-lit dinner and breakfast plus a guided tour of the mine's winding galleries, vast caverns and lakes.
You'd be forgiven for thinking you were sea-ing things - but this cliff-top cruise ship hotel in South Korea is the real deal, and a world first. The Sun Cruise Resort and Yacht in Jeongdongjin, South Korea, has become one of the country's biggest tourist destinations, and is described by Visit Korea as "the world's first on-land cruise themed resort". The resort gets four out of five stars on Tripadvisor, with one traveller from Northern Ireland writing: "The sight of a cruise ship on the top of a cliff is breathtaking! You can hardly imagine it is possible, so staying here is a very unique experience. "The piped soundtrack of bird calls and breaking waves adds to the illusion of being at sea. Thankfully though, the boat does not rock!"