The world is full of strange places, so why not strange hotels? You will not likely find any of these in the most recommended section of even the best hotel portals as they are not for the average traveller.
Jules Undersea Lodge, Key Largo, Fla. 
You can almost imagine this place like the isolated research labs in the DOOM movie and it actually is a former research lab located underwater. Those who cannot scuba dive can forget about staying here although you only need to dive 21 feet to reach their main lobby. This hotel can house a whooping 6 guests but, listen to this, each room is air-conditioned and contains a full 42-inch window in the water. Better draw the shades if you don’t want fishes and other deep-sea creatures peeping in on you!
Hydropalace, Qingdao, China.
This most unique hotel is anchored in the Yellow Sea where it is 16-20 meters deep during low tides. How do you get there? By a yacht of course!
Ice Hotel, Quebec, Canada.
This hotel is probably most well-known among all the rest on this list no thanks to James Bond. This freezing hotel is reconstructed each year out of 15,000 pounds of snow and 500 pounds of ice. The 34-room hotel features an ice chapel, two art galleries and a host of outdoor activities. Surprisingly, the temperature inside the hotel is not arctic cold, but hovers around 23 to 28 degrees Fahrenheit, and best of all, the beds are carved from ice. Don’t worry, you don’t sleep directly on the ice, though–there’s a wooden plank between the ice and a comfy mattress, plus you’re insulated with a special sleeping bag that can withstand the harshest temperatures (-40 degrees Fahrenheit). The best thing about this place, the bathrooms are heated!
Casablanca Hotel, New York City.
This Casablanca Hotel is named for the classic 1942 film featuring Humphrey Bogart and Ingrid Bergman.
Propeller Island City Lodge, Berlin, Germany.
Each room features a different theme from coffins to castles. There is even a room (as seen below) with wooden blocks adorned with 300 different symbols, talk about unusual.
Library Hotel, New York City.
No prizes for guessing what this hotel is unusual for. It is located, (surprise!) near the New York Public Library. Each of its 10 floors is designed after one of the 10 categories of the Dewey Decimal System, such as Math and Science and Religion, and each room houses part of the hotel’s collection of 6,000 books. Think Nerd paradise.
The Pitcher Inn, Warren, Vt.
The nine rooms and two suites at The Pitcher Inn are designed on themes such as “School,” “Trout” and “Calvin Coolidge.” And the themes are not limited to just variations in wallpaper–the “Stable” suite has a hay chute opening into it.
Ariau Towers Hotel, Brazil.
Ever dreamed of sleeping on the treetops since you were young, but could not build a treehouse near your home? This is your dream come true. This hotel is situated in the treetops of the Amazon Rainforest with “Tarzan’s house,” perched on stilts 80 feet above the ground. This sounds cool!
Beckham Creek Cave Haven, Parthenon, Ark. 
Think Bill Gates during caveman times and you get Beckham Creek Cave Haven. This ultimately “luxurious cave” features jacauzzi bathtubs and large windows for lighting.
Winvian, Morris, Conn.
The most unique feature of this place, is the lodging options, one of which is a helicopter. Don’t ask me, but it doesn’t sound like the most comfortable room!
