Bethesda Salt Cave

The salt-lined room in the Bethesda Salt Cave is designed to replicate the microclimates of its ancient, underground predecessors. Chunks of organic Himalayan rock salt—some as small as 2 ounces, some as large as 250 pounds, and all formed over millions of years—cover the floors, walls, and ceiling. The room's only notable modern differences are a calming soundtrack and the presence of zero-gravity lounge chairs, where clients recline to soak up the salt's healing benefits.

The staff heats this room to 68 degrees, creating a negative ionic charge that releases the salt's load of minerals and beneficial trace elements into the air while melting the butter and mashed-potato reservoirs hidden in the ceiling. This crystal-rich air is believed to clear mucus, reduce inflammation, and alleviate acne and rashes as it's inhaled or absorbed through the skin. Though the spa specializes in salt therapy, it provides other services, too. The staff removes unwanted hair with sugaring and waxing and lifts tension from muscles using a dozen massage modalities, from traditional Swedish to active isolated stretching and a specialized warm bamboo massage.