Zao Onsen

The bus from Yamagata Station takes forty minutes to climb from the flat Yamagata Basin up the switchbacks to Zao Onsen village, and the elevation change is abrupt enough that your ears pop twice before you arrive. The village sits at about 900 meters, high enough that the snow comes early and stays late, and the buildings here have the thick-walled, heavily insulated look of structures that have been built to survive being completely buried. In winter the ski slopes above town operate well into April, and the ropeway that runs to the summit crater of Zao-san gives access to the phenomenon that makes this mountain internationally photographed: the juhyo, or snow monsters, which are the ski run spruces after weeks of wet Pacific snow has frozen around them in successive layers until each tree becomes a shapeless white mound three or four meters tall, standing in rows across the high slopes like an army of something out of a fever dream.

The water at Zao Onsen is among the most chemically aggressive in Japan. The springs are sulfur and strongly acidic, with a pH that sits at approximately 1.2 to 2 depending on the source and the season. At that acidity the water will corrode metal left in contact with it, and signs at every bathhouse remind you to remove all jewelry and watches before entering. The water itself is a milky opaque white with a sharp, clean sulfur smell that fills the bath halls. When you lower yourself in, the initial sensation is a faint tingling across your whole skin surface, not painful, more like mild carbonation working from the outside in. The temperature at the Dai-rotenburo, the large outdoor communal bath built from stacked natural stone along a mountain stream, runs around 45 degrees Celsius, and the combination of that heat and the acidity means you will come out pink and scrubbed-feeling and absolutely warm in a way that takes a long time to fade.

The Dai-rotenburo holds up to 200 people and is open spring through autumn, closing when the snow covers the stone walls entirely. In summer it is the social heart of the resort, a vast open-air pool under the sky with steam moving across the surface and the sound of the mountain stream running alongside. The bath is free-form, built into the hillside rather than excavated, and the irregular stone walls give it the feeling of something natural rather than constructed. The sulfurous white water obscures everything below the surface immediately, which produces an odd sensation of floating in opaque cloud rather than sitting in a pool.

In January and February, if you take the ropeway at first light on a clear morning, the juhyo are backlit by a low sun and the whole landscape above 1,500 meters looks monochromatic and prehistoric. The trees are unrecognizable as trees. You ride back down on the cable car, walk through the village to the public bath, step through a wooden door into the warm sulfur air, and lower yourself into water that is dissolving the mountain from below at the same time the mountain above is disappearing under twenty tons of ice. Zao is not a subtle place, but it earns every one of its extremes.