The Turkish steam baths called hamams first gained a following during Ottoman rule in the 1400s.
They are popular once more.
Inspired by the Roman thermae, they feature multi-room experiences which traditionally start with the camegah, an entrance where guests sip a soothing beverage, before moving on to a heated dry iliklik which allows for acclimatisation of temperature, and then a sicaklik, or humid room, where guests are scrubbed down on marble stones.
The ITC Grand Bharat, which opened in May in Gurgaon, India, features Persian-influenced hamam therapies which can be traced to the Mughal era, including a 70-minute ritual which uses steam and a rich soap with a massage, followed by a body exfoliation (about US$130 or S$175).
Because many hamams are architecturally elaborate and require significant investment, some spas offer treatments inspired by hamams instead of the more traditional multi-room therapies.
A new Red Flower treatment at Eau Palm Beach Resort in Florida is a 90-minute purifying ritual which involves being wrapped in a cocoon made of a clay called rhassoul (US$295).
The Four Seasons Doha in Qatar has a Moroccan-inspired treatment with a mint foot scrub, an exfoliating body polish with date seeds, a pink clay body mask and a scalp massage (about US$380).
Some spas have invested in humid chambers where guests can unwind. The Mandarin Oriental, Las Vegas, has a unisex steam chamber for up to eight guests to receive a ritualistic scrub down.
Villa Stephanie, the Brenners Park-Hotel & Spa in Baden-Baden, Germany, includes a hamam surrounded by a private park.
The recently reopened Condado Vanderbilt Hotel in San Juan houses Puerto Rico's first hamam.
Ms Beth McGroarty, a research director at the Spafinder Wellness company, said the trend has taken off at resorts and spas at an unexpected pace. "They have gone from novelty to almost ubiquity at the big, important new spas," she says.
New York Times