Infinitely more happening than its younger brother Costes K in the 16th, Jean-Gilbert’s jewel remains an A-List address even after a decade of hype. More for posing than pampering, with style trumping substance. Regular rooms are suitably boudoir chic but can be smallish. Suites are searingly seductive. Jacques Garcia’s bar/resto/lounge, with its swaggy splendor and neo-Napoleon III accents, is an immense draw. Don’t miss the indoor pool, which pulses with a submarine sound system. €280–€2000+