Spas with upscale

Karlovy Vary, Karlovy Vary Region

Adults-only resort spa on the Březová reservoir near Karlovy Vary, open to hotel guests only, with a two-floor wellness centre and outdoor baths.

Los Angeles, California

A hotel spa at Shade Hotel Redondo Beach with sauna, steam, pools, cold plunge and thermal circuits, open to hotel guests overlooking the marina.

Los Angeles, California

Hotel pool and hot tub deck at a Tapestry by Hilton near SoFi Stadium and the Kia Forum in Inglewood, open to registered guests only.

Arima Onsen, Hyogo

Hotel spa in Arima Onsen with Arima's rare iron-rich "ginsen" waters, outdoor baths, sauna and jacuzzi, run as an all-inclusive overnight stay.

San Diego, California

Hotel spa at Carté Hotel San Diego Downtown with a heated saltwater pool, whirlpool, 28,000 sq ft fitness club with sauna and steam room, open to guests only.

Oaxaca

An all-inclusive beachfront resort spa in Huatulco with a sauna, steam room and thermal pools, open only to hotel guests.

Miami, Florida

A hotel spa at Eden Roc Miami Beach in Mid-Beach with sauna, steam room, cold plunge and thermal circuits, open to resort guests only.

Kamijima, Ehime

An all-inclusive resort on Yugejima island in Setouchi's inland sea, with ocean-view outdoor baths, ocean-front rooms, and a day-pass option.

Afyonkarahisar

Resort hotel in Afyonkarahisar built around thermal pools, spa treatments and physical therapy, open to hotel guests.

Spa, Liège

Hotel spa in the town of Spa, Belgium, with a thermal pool, relaxation lounge and restaurant, open to day-pass visitors, not just hotel guests.

Catskills, New York

A Catskills retreat center with a Tibetan-style spa offering sauna, steam, pools and cold plunge, built around overnight stays and group programs.

Kyle, Texas

A 88-acre Hill Country resort near Kyle and Wimberley with overnight rooms, a garden spa, pool, hot tubs and day-pass access by reservation.

San Diego, California

A hotel spa on Mission Bay in San Diego with sauna, steam room, cold plunge and thermal pools, open only to resort guests.

Ein Bokek, Southern District

A large hotel resort spa in Ein Bokek with two spa facilities, a thermal pool and 606 rooms overlooking the Dead Sea, open to hotel guests only.

Atami, Shizuoka

A hotel spa in Atami with a thermal onsen pool, open only to overnight guests staying at Fufu Atami.

Catskills, New York

Adults-only resort spa in the Catskills with sauna, hot tub, yoga studio and overnight stays for hotel guests only.

Santa Barbara, California

A hotel spa inside Hotel Californian in Lower State, Santa Barbara, with a thermal pool and relaxation lounge, open to hotel guests only.

Scottsdale, Arizona

A resort spa at JW Marriott Phoenix Desert Ridge with a thermal pool, relaxation lounge and on-site café, open to hotel guests and day-pass visitors.

Austin, Texas

A lakeside resort spa on Lake Travis in Lakeway, Texas, with pools, outdoor baths and treatments, open only to hotel guests.

Bad Blumau, Styria

Rogner Bad Blumau is a Hundertwasser-designed thermal resort in Styria with geothermal pools, outdoor baths and hotel-guest-only access.

Carmel-by-the-Sea, California

A golf-and-wellness resort spa in Carmel Valley, open to hotel guests only, with a heated pool, fitness cabanas and treatments at Spa Adeline.

Sedona, Arizona

A boutique resort spa in Sedona with a heated pool, hot tub, yoga and massage, open only to hotel guests.

Islamorada, Florida

Hotel spa at Three Waters Resort and Marina in Islamorada, Florida, with outdoor baths, a pool and ocean views, open to resort guests.

Yufuin, Oita

A small hillside ryokan near Yufuin's town center where every room has its own half-open-air bath filled with 100% source hot-spring water and a view of Mt.