Banyan Tree Bahrain, Juffair
This new resort in a fledgling suburb has a 100,000-square-foot spa that is a Xanadu for grown-ups: Millions of glittering tiles decorate the walls of rooms offering a collection of water therapies (ice igloo, brine cavern, steam grotto, medium-hot saunarium, and monsoon showers with light and sound effects). All 12 private spa pavilions have humongous baths, gardens, and glassed-in wet rooms; four couples pavilions can be rented for overnight stays. Spend an hour in the Hydrothermal Garden ($113), a large scalloped pool with nine bubble, jet, and resistance current stations next to a wet maze of 15 domed chambers that are visited in sequence for steaming, showering, and mud- and salt-scrub slathering. Plus, there's the region's largest modern hammam (massages, $120).