Tayka Hotel de Sal Where:Tahua, Bolivia How much:about $95 a night Why it's cool:You've stayed at hotels made of brick or wood, but salt? That's something few can claim. Tayka Hotel de Sal is made totally of salt--including the beds (though you'll sleep on regular mattresses and blankets). The hotel sits on the Salar de Uyuni, a prehistoric driedup lake that's the world's biggest salt flat. Builders use the salt from the 4,633squaremile flat to make the bricks, and glue them together with a paste of wet salt that hardens when it dries. When rain starts to dissolve the hotel, the owners just mix up more salt paste to strengthen the bricks. Green Magic Nature Resort Where: Vythiri, India How much: about $240 a night Why it's cool: Riding a pulleyoperated  lift 86 feet to your treetop room is just the start of your adventure. As you look out of your open window--there is no glass--you watch monkeys and birds in the rain forest canopy.  Later you might test your fear of heights by crossing the handmade rope bridge to the main part of the hotel. You don't even have to come down for breakfast--the hotel will send it up on the pulleydrawn "elevator". Dog Bark Park Inn B&B Where: Cottonwood, Idaho How much: $92 a night Why it's cool: This doghouse isn't just for the family pet. Sweet Willy is a 30foottall dog with guest rooms in his belly. Climb the wooden stairs beside his hind leg to enter the door in his side. You can relax in the main bedroom, go up a few steps to the loft in Willy's head, or hang out inside his nose. Gamirasu Cave Hotel Where: Ayvali, Turkey How much: between $130 and $475 a night Why it's cool: Experience what it was like 5,000 years ago, when people lived in these mountain caves formed by volcanic ash. But your stay will be much more modern. Bathrooms and electricity provide what you expect from a modern hotel, and the white volcanic ash, called tufa, keeps the rooms cool, about 65degFin summer. What is the similarity of the four hotels?
Being old. Being unique. Being natural. Being beautiful.