Spas with reservation required

Los Angeles, California

A medical spa in Silver Lake, Los Angeles offering body contouring, massage, hair removal and skin treatments in private suites, open daily 9am to 10pm.

Hudson Valley, New York

An outdoor spa on the Hudson River in Kingston, NY, with two waterfront barrel saunas and garden massage cabins, reservation required.

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.

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.

Asheville, North Carolina

An overnight-stay forest retreat near Fairview with private cedar hot tubs and a shared sauna pavilion session, not a drop-in day spa.

The Hamptons, New York

A moderate-priced, adults-only day spa in Hampton Bays focused on massage, with a salt room and red light therapy, by appointment only.

Penang

An adults-only villa resort spa near Kepala Batas, Penang, with 18 private villas, spa treatments and plant-based dining; reservation required.

Bad Blumau, Styria

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

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.

Big Sur, California

Adults-only hotel spa at Ventana Big Sur with ocean-view treatment rooms, outdoor cabanas for couples, and a 24-hour fitness and yoga space.