Wind deep into the mountains for an onsen
Hikyo onsen, hidden hot springs, are rustic inns deep in the mountains, often the only building in sight. Getting there is part of it: you wind up mountain roads or ride a cable car down into a gorge, then soak in water that comes straight from the ground. Many close on set weekdays or are cut off by snow in winter, and not all take day visitors, so check before you go.
The oldest inn in the Nyuto Onsen area in the mountains of Akita, northern Japan, where low thatched-roof buildings stand among the trees. Four springs rise near the inn, called white water, black water, middle water and waterfall water, and you can compare them in one visit. Day bathing is closed on Mondays for cleaning.
An inn on a cliff above the Iya Valley in the mountains of Shikoku, where a small cable car takes about 5 minutes to run down a steep slope to outdoor baths beside the Iya River. You soak in spring water that flows straight in, looking up at the forested walls of the gorge. Day visitors are welcome except on Wednesdays, and the cable car ride is included.
A lone inn at the foot of the Hakkoda Mountains in Aomori, northern Japan, where snow piles up about 5 meters deep in winter. The water rises through the floor of the bath itself, and you can compare the lukewarm lower bath with the hotter, milky upper bath. You can drop in without booking, but from November to the end of April it is closed on Tuesdays, Wednesdays and Thursdays.
A lone inn about 150 years old in the mountains of Minakami, Gunma, whose wooden bathhouse, Hoshi-no-yu, is a registered cultural property. Hot water bubbles up between the round stones on the floor of the bath, which is mixed (konyoku, shared by men and women), and bathing wraps are not allowed. Day visitors are accepted only from late morning to early afternoon.
An inn in the forested Hakkoda Mountains of Aomori that calls itself a thousand-year hidden spring. In its Kyuan-no-yu bath, the water flows straight from the spring and out again without being reheated or recirculated. Mountain roads here can close in late autumn and winter, and the inn may close for the season, so check its official site before you plan a trip.