The Hobbits House in the Cotswolds was a sheep shed. Built without permission by a local artist, the sprawling construction took nearly ten years to build. Abandoned in the 1990s. See the Flickr website for more pics: www.flickr.com/... .
This is both a restaurant and a place to spend the night. You hike up to it with a backpack and warm clothes. It is open only warmer months, great Swiss food, no shower, and you share a room with others. Check it out on TripAdvisor.