Loaded with major ions — the essential minerals (Ca, Mg).
Buoyancy
Standard buoyancy
LowHigh
Soft water — natural, classic buoyancy.
CalciumSulfatesMagnésium
Yutsubo Onsen—the Bath Vessel Spring—emerges in Oita Prefecture, Japan's undisputed onsen capital where more thermal spring water flows per day than anywhere else on earth, and every valley and hillside seems to offer a new discovery of mineral-rich waters. The evocative name suggests a spring contained like precious water in a carefully tended vessel, an image that speaks to the Japanese ideal of the bath as a ceremonial, almost sacred space worthy of deep attention and respect. Sulfated waters bring the mineral richness typical of Oita's volcanic geology, providing the skin-conditioning and circulation-stimulating properties that draw visitors to this corner of Kyushu.
Insider tip — Yutsubo Onsen in the Oita highlands lies near Yufuin and Beppu in Japan's hot-spring capital — the prefecture with more thermal springs and greater hot-water output than anywhere else on Earth, where steam rises from the ground across entire towns. The calcium-sulfate springs draw on the extraordinary geothermal energy of central Kyushu, serving a landscape where hot-spring bathing is the defining cultural feature, home to the famous Beppu 'hells' and the elegant Yufuin resort beneath the twin peaks of Mount Yufu.
