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).
800/742-9000 or 413/637-4100; www.canyonranch.com