What can you say about a place that has lent its name to the English lexicon? This 136-room hotel, opened by the eponymous César in 1906, has a spectacular position overlooking Green Park and is supposedly the Royal Family’s home away from home. (It is very close to the palace.) All rooms have Louis XVI–style interiors and antique furniture.
Various formal-dress and smart-casual codes (shirt and tie) apply in some of the hotel's outlets. For stunning cocktails in art deco opulence, take a seat in the Rivoli Bar.