Courtesy Park Hyatt

This hotel used sleek design to raise the bar for Colorado ski spas when it enlarged its Allegria spa from 17,000 to 30,000 square feet last year. Twenty-three-foot-high ceilings give the entrance hall the feel of a stage set, and large, well-proportioned windows allow natural light to pour into the treatment rooms, a rarity in most ski spas. The materials — maple and walnut, wrought iron, and glass panels etched with an aspen-tree motif — are mountain-sensuous. (Right, the inviting relaxation room.) The main attraction is the 2,600-square-foot Aqua Sanitas ("Healing Waters"), a classic hydrotherapy sequence, from caldarium (hot room with a soaking pool) to tepidarium, a Pompeian womb with heated tiled chaises. You could easily spend half a day in this spa, and indeed, room service is kept busy delivering lunches here. — E.P.

800-223-1234, Park Hyatt Beaver Creek