Sandwiched between a modern-looking roof and an expansive deck about an hour outside of Paris is a very traditional wood cabin called La Fuste. The walls are solid timber, there’s no water or electricity, it’s heated by a woodstove, and the toilets are outside. Showers? Well, those are in the castle . . . the 500-year-old Château de Graville, which dominates the property on which La Fuste and six treehouse-style cabins are available for rent. The 215-square-foot Fuste goes for about $150 a night and is completely isolated from the castle and the other guesthouses in a slice of French forest filled with free-roaming horses and songbirds.