Fushime Onsen is a hot spring town in Kagoshima, Japan. The water leaves the ground at 100°C, hot enough that it has to be cooled before anyone can get in. Officially the water is classed as chloride spring.
Salty water. The salt leaves a thin film on the skin, so you stay warm well after leaving the bath.
More photographs
From Wikimedia Commons. Tap a photo for the photographer and licence.
With tattoos
Many public baths still turn away visible tattoos, and the rule is set by each bath, not by the town. The reliable way round it is to bathe privately: a room with its own open-air bath, or an inn with a private bath you can book for yourselves.