Courtesy Four Seasons

This sumptuous spa offers one of the city's greatest luxuries: space. The soaring reception area is sun-splashed, the harbor-view couple's suites could double as guest rooms, and the sophisticated hydrotherapy suites are 21st-century Roman baths writ extra-large. Services live up to their surroundings: well-executed treatments with Futuresse, Natura Bissé, and Just Pure products, plus terrific yoga and tai chi classes. — A.A.

800-332-3442, www.fourseasons.com