The World's Coolest Spas

Calistoga, California (indianspringscalistoga.com)

Why It Rocks: After a strenuous day of wine tasting in Napa, we'd be content to cool our heels here. Wapoo Indians praised the area's therapeutic thermal geysers 8,000 years ago, and today, fatigued Hollywood execs still swear by them.

Signature Service: The Volcanic Ash Mudbath ($85) starts with a superthick (and slightly stinky) heated mud soak, followed by a purifying eucalyptus-and-lavender steam, and ends with a warm-blanket-wrapped 15-minute power nap in a private nook.

Kuwait City, Kuwait (hotelmissoni.com)

Why It Rocks: Colorful Italian design meets the Middle East. The holistic spa tucked in the brand-new Missoni hotel overlooks the Persian Gulf and makes use of local indulgences like organic dates and olives and delicious-smelling native spices, such as crushed cinnamon and dried coffee.

Signature Service: Be pampered like an Arabian princess — literally — with the Gulf Spices Ritual (approximately $300), a vigorous dry body brushing session followed by a ginger-and-sea-salt-infused bath and detoxifying frankincense-oil massage. Don't forget to grab a delish Dolce Fico drink made with fig, honey, cream, and raspberry-infused water on your way out the door.

Santa Fe, New Mexico (tenthousandwaves.com)

Why It Rocks: This traditional Japanese-style onsen bathhouse and ryokan (inn) nestled in the Sangre de Cristo mountains quirkily throws a touch of the Southwestern adobe aesthetic into the mix.

Signature Services: Indulge on a mind-blowing Yasuragi Head & Neck Treatment using pressure-point massage with warm camellia oil ($65), or enjoy a soak on the cheap ($25) in the clothing-optional communal tub. (Beware the naked hippies!)