Uozu Onsen

Uozu Onsen serves a coastal city on Toyama Bay famous for two extraordinary natural phenomena — the spring mirage season when the atmospheric conditions over the bay produce spectacular superior mirages (fata morgana) that cause islands, mountains, and even ships to appear inverted or floating above the water, a phenomenon that has been documented and celebrated in Uozu for centuries — and the firefly squid season from March to May when the Toyama Bay's upwelling currents drive vast numbers of bioluminescent hotaru-ika to the surface in a blue-glowing spectacle visible from shore on moonless nights. Uozu Castle ruins overlook the city from a small hill, and the city's museum of the mirage phenomenon documents the atmospheric optics of this Japan Sea coast specialty with scientific precision. The onsen's siliceous mineral waters, drawing from the geothermal resources of the Toyama coastal geology, provide warm therapeutic bathing in a city whose combination of atmospheric mirages and biological bioluminescence creates one of Japan's most optically and naturally spectacular coastal environments.