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Towada-Hachimantai NP, Iwate
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Matsukawa's geothermal steam both fixes dye and, through trace hydrogen sulfide, bleaches parts of the cloth. Developed locally in 1981, GEOCOLOR's unique process creates gradients shaped by the area's volcanic steam.
In 1952, a well drilled at Matsukawa for hot-spring development unexpectedly vented steam. That discovery led to geothermal exploration and, in 1966, Japan's first commercial geothermal power station, just upstream.
At Kyo-Unso, dinner can feature horo-horo (guinea fowl) hotpot—a surprising mountain-inn specialty—alongside grilled iwana char and seasonal mountain fare. Spring brings wild greens; autumn brings mushrooms.
On February 18, 2026, IEEE named Matsukawa a Milestone, recognizing its historic engineering impact. Experience here improving geothermal turbines also helped advance reliability across thermal and nuclear power equipment.
Matsukawa was recorded as an officially registered hot-spring resort in 1743, but local roads were not paved until 1970—227 years later. That gap gives a concrete sense of how secluded this mountain valley remained.
Japan's Geothermal Power Generation Day falls on October 8—the date Matsukawa's station began commercial operation in 1966. The anniversary was designated in 2016, marking the plant's 50th year.
Matsukawa uses Japan's only steam-dominated geothermal reservoir: natural steam drives the turbine directly, without first separating it from hot water. That makes its system unusually simple.
At Matsukawa-so, the baths draw natural spring water, while the nearby geothermal plant supplies electricity and steam for room heating, kitchen hot water, and snowmelt. Volcanic heat quietly helps with the inn's everyday work.
Kyo-Unso's sulfur-rich water is so corrosive to metal that the inn has no showers or boiler. Instead, guests rinse by scooping hot water from a trough—a small daily adaptation to Matsukawa's volcanic chemistry.
To reduce impacts on Towada-Hachimantai National Park, Matsukawa's steam wells angle underground from inside the station grounds. The Cultural Affairs Agency cites this as one of the plant's environmental design choices.
The winter bus route to Matsukawa Onsen has had an old-fashioned answer to the steep, icy climb: a four-wheel-drive bonnet bus, because an ordinary route bus can struggle on snow-covered slopes.
