Iruma Onsen
- Location
- Iruma, Saitama, Kanto, Japan
- Water type
- sodium chloride
- Temperature
- 41 °C
- pH
- 7.3
Water profile
Relaxing — deep, immediate muscle release.
Loaded with major ions — the essential minerals (Ca, Mg).
Dense, salty water — you float without effort.
Iruma Onsen lies in a western Saitama city best known for the Iruma Air Self-Defense Force Base, whose annual air show draws hundreds of thousands of spectators from across the Tokyo metropolitan area to watch precision flying demonstrations by Japan's Blue Impulse aerobatic team and displays of military aircraft rarely seen up close by the public. The Sayama Hills, a range of low forested ridges extending across the Iruma-Tokorozawa border, form one of the last significant green belts of natural woodland accessible to residents of the sprawling Tokyo megalopolis, providing habitat for woodland species and walking trails that thread through surviving secondary forest. The onsen's warm mineral waters offer urban residents a rare moment of thermal relaxation close to both military spectacle and one of the Tokyo region's most valued natural retreats.