Niche marketing has always been an interesting field. No matter how bizarre or narrowly focused some things might seem, there's someone who finds it perfect. Unusual Hotels of the World clues into this phenomenon.

Take an ice hotel, for example. I could stay just about anywhere for a night, but an ice hotel ... well, let's just say one night would be it for me. Or what about underwater hotels?

If staying in someplace beyond the norm is what you crave, take a look at Unusual Hotels of the World. This wildly inventive site offers more than 130 "hotels" around the globe. I use the term "hotels" loosely because one of the places offered is the Woodpecker Hotel in Sweden, a tree house that holds just one party at a time in a 300-year-old oak tree. Tree houses seem to be pretty popular; there a quite a few on the list.

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