In this city that prides itself on luxury shopping, an Italian prestige brand rules at the spa. While the 12,000-square-foot facility offers everything from facials to Vichy showersincluding a "Margarita Salt Glow" scrub ($170)its Prada treatments are the most popular. The line's Body Facial ($375) includes a crystal exfoliation, allover mask, shower, and massage using the lightly scented products. Best of all, most Prada treatments include an eight- or nine-day take-home supply of products. The separate men's and women's lounges offer a steam room, a sauna, a whirlpool, and special-healing-waters showers, as well as access to the hotel swimming pool (massages, $120$140).