The original fort (built in 1666) was later remodelled as an inn but was then abandoned for many years. This is a dramatic but dead-basic spot that’s essentially 'camping with walls': you sleep in rooms, but must bring all your own linen, food and drinking water. Wonderful bucket-nozzle showers from cistern water are on offer; bathrooms are shared.
Payment is inconveniently required in advance via bank transfer, but the outlook and nature experience is simply beautiful. Bring a torch, as the generator goes off at midnight, and keep in mind the fort is reachable only via a 45-minute, 360-step hike or by water taxi (€3).