河内温泉 is a hot spring town in Kumamoto, Japan. Officially the water is classed as simple spring and chloride spring.
Mild and low in dissolved minerals. Usually clear and gentle on the skin, which is why these baths are often recommended for first-timers.
Salty water. The salt leaves a thin film on the skin, so you stay warm well after leaving the bath.
Planning a first soak? Read how an onsen stay works, and what to do if you have tattoos.