Indian Springs, Calistoga, CA

There’s no better way to warm up, literally and figuratively, for an amorous evening than with a soak in steamy water so rich with minerals it feels like silk ― especially when your private cottage is just footsteps away. To make it even more interesting, try Watsu on each other in the pool. Wat-what? Enthusiasts claim that this aquatic massage technique ― which involves rocking and cradling ― promotes a blissful sense of letting go. $$$ (ask about winter Sun–Thu spa packages); indianspringscalistoga.com