Okumizuma Onsen
- Location
- Kainan, Wakayama, Japan
- Water type
- bicarbonate, carbonated
- Temperature
- 40 °C
- pH
- 6.3
Water profile
Relaxing — deep, immediate muscle release.
Loaded with major ions — the essential minerals (Ca, Mg).
Mineralised water — eases movement and joints.
Okumizuma Onsen is a bicarbonate and carbonated thermal spring in Osaka Prefecture, making it one of the more unusual mineral spring finds in Japan's most urban and densely populated prefecture—a reminder that even beneath Osaka's extraordinary commercial energy and urban infrastructure, geological thermal activity can push mineral-rich carbonated waters to the surface. The effervescent, skin-stimulating quality of naturally carbonated bicarbonate springs provides a therapeutically refreshing contrast to the pace of urban Osaka life, where the daily rhythms of commerce and consumption are among the most intense in Japan. This spring represents the unexpected natural richness that can persist beneath Japan's most densely developed urban environments.