Lake Shima

Fed by mineral-rich waters from Shima Onsen, this small reservoir glows an otherworldly cobalt blue that shifts intensity with sunlight and season. Kayak and canoe rentals let you paddle directly over the luminous surface, and the surrounding forest keeps the shoreline undeveloped and quiet. The color is most vivid in early morning before wind ripples the surface, creating mirror-like reflections of the enclosing mountains.