Very cool and unusual hotels. Need some place to stay? Have a lot of money?→[More:]
You could stay in a Treehouse in India. "Bamboo and Rope Tree houses 15 meters high in a private wildlife reserve with en-suite toilets and hot water. Wild Canopy Reserve provides rich wildlife and multi-cuisine food, in a truly wonderful wilderness experience."

Or 40' underwater at The Poseidon, in your very own pod in a 5,000 acre Fijian lagoon. It's not built yet, and is supposed to open in 2009. Website is Flash and sound.
For qualified divers, also see Jules Undersea Lodge. official site.

Finally, "The Library Hotel in New York City is the first hotel ever to offer its guest over 6,000 volumes of books organized throughout the hotel by the Dewey Decimal System."