Letham, United Kingdom
The treehouse on the grounds of Fernie Castle
won't ever let you forget it's, well, on the grounds of a castle. Ever. For one, it sports a castle-worthy turret and arched front door. But if that's not enough, indoor murals depicting the castle in the distance serve as reminders. Bookable for an overnight upon request, the treehouse comes with amenities such as a fridge stocked with champagne and chocolates. It's tough living like royalty.