Sagashio Onsen

Sagashio Onsen—the Searching Salt Spring—is a saline thermal spring in landlocked Yamanashi Prefecture, a geological curiosity in a mountain prefecture entirely surrounded by highland terrain far from the nearest coast, whose saline character speaks to the ancient marine sedimentary formations buried beneath the Kofu Basin that preserve the mineral signature of a sea that covered this inland landscape millions of years before the uplift of the surrounding mountain ranges created Japan's current topography. The sodium chloride mineral content makes saline springs excellent heat-retaining baths (the quality called yudamari in Japanese balneology), deeply warming the body with a mineral efficiency that simple alkaline springs cannot match—a particular asset in Yamanashi's highland winters. The searching-salt name captures the geological quest implied by the presence of marine mineral water deep in the Japanese Alps, where the memory of ancient seas persists in the mineral character of the volcanic earth.