Spas with reservation required

New York City, New York

A small Japanese-style bathhouse near Union Square with sauna, hot-tub onsen, cold plunge and a recovery lounge, open by reservation only.

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.

Penang

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

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.

Miami, Florida

Recovery and longevity studio in Brickell offering sauna, cold plunge, cryotherapy and IV therapy, bookable by reservation or walk-in.