Amberley Castle, Sussex, England
Every evening, just before midnight, the enormous Portcullis at Amberley Castle is lowered to enclose the medieval property within its 60-foot protective wall. Built in 1100 by Henry I, the castle boasts an ownership that reads like the history of England itself. Passed from blue blood to blue blood, to the church and back to the royals, the castle landed with Elizabeth II, who sold it to a private owner in 1982. Purchased by Brownsword Hotels in 2011, it lives on as a Relais & Chateaux destination with 13 rooms and six suites. The luxury hotel also boasts an unusual event space near its entrance—a treehouse called Mistletoe Lodge built within the branches of a stand of poplars. Rooms, from $500; amberleycastle.co.uk.