Shima Onsen

Hot spring town in Gunma Prefecture's mountains, claiming the distinction of being Japan's first onsen officially certified for its mineral waters, a designation granted over 400 years ago. The name comes from an archaic reading of 40,000, referencing the ailments the waters are said to cure. Traditional wooden ryokan line the narrow valley, and the Sekizenkan inn, with its red-lacquered bridge and tunnel passageways, is said to have inspired the bathhouse in Hayao Miyazaki's Spirited Away. The surrounding gorge has scenic walking paths, and Okushima Lake glows cobalt blue in a way that feels almost unreal.