Spas with cold plunge

Reykjavik, Capital Region

Eight oceanfront geothermal pools in Hvalfjörður, 45 minutes from Reykjavík, plus steam baths, a bistro and guest houses for rent.

Pagosa Springs, Colorado

Victorian-style bathhouse in downtown Pagosa Springs with mineral soaking tubs, a rooftop tub, sauna, cold plunge and on-site massage.

Shibu Onsen, Nagano

Reservation-only private hot spring and sauna suites at a Nagano brewery complex, built around a craft beer bathing plan for two to four guests.