Concierge.com's insider take:

The Çırağan Kempinski must have been glancing nervously over its shoulder in June 2008, when the new Four Seasons Bosphorus opened in the elegant 19th-century Atık Paşa Palace right next door. Would the upstart steal its crown as the city's sultan of waterside luxury? The answer: not quite. While the new Four Seasons definitely rivals the Kempinski in opulence and service, it stops short of outshining its neighbor. In contrast to the compact elegance of the city's first Four Seasons—a 15-minute cab ride away in the old city of Sultanahmet—the chain's new location on the banks of the Bosphorus compensates for its peripheral address with bags of breathing space and a killer view. Ogle at the picture-perfect tableau of exterior poolside gardens set against the building's molded ivory facade, but avert your eyes from the painful sight of the two auxiliary wings, which contain most of the hotel's low- and mid-range rooms. The decor throughout is tasteful but humdrum, with muted tones of cream, beige, and brown and only a light sprinkling of Turkish motifs—a relief to some, a disappointment to others. If you're ready to shell out a few hundred euros extra, treat yourself to a room or suite in the palace building itself, where high ceilings and enormous windows offer a full frontal view of the Bosphorus—and the most romantic night in the city. (Rooms in the modern wings have at best partial views of the water; some overlook a brick wall and the adjacent high school.) Service is excellent, verging on obsequious (prepare to be addressed in French upon your arrival), and the hotel's in-house restaurant, Aqua, is worth a visit for chef Fabio Brambilla's Mediterranean fish fare. Make time for the spa here: The pillared underground swimming hall (swim underwater to hear classical music piped through the pool) and hammam offer an easy morning's pampering.