In 2007 the Palacio de Sal, a 16-room hotel, went up on the eastern "shore" of Bolivia's Uyuni Salt Flats. Because timber and other building materials are not locally abundant, the building is constructed primarly of salt. Roughly one million salt blocks comprise the floors, walls and ceiling, as well as beds, tables and seating surfaces.
In addition to lodger's rooms, the Palacio de Sal is kitted out with lounging areas, a spa, dining facilities and even a golf course.
This is actually the second incarnation of the Palacio de Sal. An earlier version was built in the '90s, but was eventually dismantled due to environmental mismanagement. As the Uyuni Salt Flats are essentially a desert, there is an issue with waste disposal—think sanitary facilities—and the first hotel reportedly skunked up the surrounding area with its human pollution. The new Palacio, however, reportedly complies with environmental regulations.
It cannot be easy to pull off efficient waste disposal at the Flats, and those trials have likely wiped out the Palacio's sole competition. Below are some photos of a competing hotel, the also-made-of-salt 27-room Hostel de Sal, which currently appears to be shut down; their web domain was abandoned at press time. Both hotels had similar prices, around US $100 per night for a single traveler.
While the still-standing Palacio offers local fare at their dining facilities, amusingly—according to Wikipedia—"There is a rule prohibiting licking the walls (in order to prevent their degradation)."
Put your tongue back in your mouth or you're going to be sorry