I can definitely say that the Das Park Hotel in Austria is the strangest hotel I have ever seen. The rooms within the hotel are made from enormous recycled sewer pipes, but are surprisingly cozy-looking.
The Das Park Hotel was designed by Andreas Strauss, who is hoping to open up more of these lodgings in different areas around Europe. The hotel is based on a "pay-as-you-wish" system with no set prices. Strauss says "We are happy to be able to provide another place for travelers, people who need a little time out from their everyday lives."