On a recent concert tour in Japan, I had the chance to visit several thermal baths and to chat with people about the tradition of bathing. I was fascinated by their differences with American spas.

Onsen are baths filled with geothermally heated, mineral-rich water. They’ve long been part of Japanese culture, but foreign travelers often struggle with the nudity aspect. - Boaz Rottem/Alamy Stock ...

It was a cold February day in northern Japan, snow piled high outside the onsen locker room windows as I slipped out of my clothes. Nervously, I stepped into the plumes of steam wafting from the next ...