The mineral hot springs in Tuscany's Val d'Orcia have been embraced for their healing properties since the days of the Etruscans. Adler Thermae makes use of these pools, along with thermal mud and steam, in all their treatments.
Signature Treatment: The Argillae-Rasul bath, which incorporates body smoothing with mineral-rich mud, an herbal steam, and a purifying bath (for up to 4 people; 45 minutes, $40 per person).
Tucked amid seven acres of tropical gardens, this beachfront resort overlooking the Gulf of Thailand uses indigenous herbs, flowers, and oils in its ayurvedic treatments.
Signature Treatment: The Revitalizing Body Cocoon, which starts with an invigorating lemongrass-spice scrub, followed by an aromatherapeutic body wrap to stimulate circulation and calm the senses. (Offered as part of Chiva-Som Spa Packages, starting at $1,650 for 3 days.)
Clays, mineral salts, and plants gathered from the surrounding red-rock desert are used in all this spa's treatments and products.
Signature Treatment: During the Painted Desert Clay Treatment, warm, mineral-rich clay is brushed lightly over the skin, then brushed away when it's dried to reveal a tighter, deeply purified complexion (1 hour, $115).
Set on 19 lakefront acres in Central Texas Hill Country, the LakeHouse Spa offers more than 100 treatments—which can be performed in private suites or outdoor cabanas.
Signature Treatment: The decadent 100-minute Gifts of Our Garden treatment, which combines a relaxing full-body exfoliation, shower, massage, and body wrap—all performed with herbs harvested from the LakeHouse's own gardens ($280).
A 3,000-acre property of landscaped gardens, organic farmland, and mountainsides crisscrossed by hiking trails surrounds this desert spa.
Signature Treatment: For the 45-minute Spring Rain Shower treatment, a detoxifying, full-body seaweed body mask is applied to re-hydrate and re-mineralize the skin. A gentle rain-like shower follows, to improve circulation (45 min, $85).
The surrounding wooded Berkshire Mountains make this 100,000-square-foot spa especially stunning in autumn.
Signature Treatment: A spa of this stature has several; try the Mango Sugar Glo, which smooths the skin with a blend of raw sugars, jojoba oil, and aloe, followed by an application of mango moisturizer (50 minutes, $140).
Set on the Yucatán's Caribbean coast, adjacent to Mayan ruins, this spa's menu incorporates traditional Mayan healing rituals.
Signature Treatment: Mayan Yoot Kene Massage, an 80-minute, full-body treatment, focuses on the abdomen—which the Mayans considered the body's "power center"—to aid digestion and balance energy ($120).
Modeled on the ancient Honjin sanctuaries of Japan, this spa—a favorite of Hollywood celebrities—hosts week-long health, beauty, and relaxation programs on its 377 rolling Southern California acres.
Signature Treatment: The 45-minute Citrus-Sea Salt Scrub with Avocado includes a full-body exfoliation with aromatic sea salts, a warm water wash, and mosturization with a citrus-shea butter body cream (part of a seven-day program, $7,750).