Spas with solo travelers

San Francisco, California

Adults-only Russian bathhouse in San Francisco's India Basin with steam rooms, cold plunge, rooftop deck and a café, open daily except Tuesday.

Istanbul

A working Ottoman hammam built in 1741 in Istanbul's Fatih district, offering traditional bath rituals with no day-pass option, only full treatments.

Saratoga Springs, New York

A floating Nordic-style sauna moored on Saratoga Lake, with a 15-person cabin, roof terrace and lake plunge, open daily except Monday.