Berggasthaus Aescher Wildkirchli

This gorgeous guesthouse and restaurant is quite literally built into a cliff, and its back wall is made up of the rock itself. 

Its precarious perch makes it difficult to get to, and it's only accessible after a steep hike along a mountain path or via cable car (the piano in the living room was brought in by helicopter). It's been around for 170 years, and was originally a home for farmers; the guestbook goes back to 1940.

Open from May through November, the guesthouse uses only rainwater, and there are no showers. Weekends often bring in rowdy groups of Swiss hikers and live music that plays late into the night. It's run by Claudia and Beny Knechtle-Wyss and their five children, plus it's home to 35 sheep, 20 rabbits, 5 chickens, 3 pigs, a donkey, and a dog.

The guesthouse (which no longer accepts guests and is now only a restaurant) is also just a short distance down the path from the Wildkirchli caves, which were inhabited by Neanderthals as far back as 40,000 years ago.  The caves later became the site of a hermitage.