Cool off in forest air after a lakeside sauna
These saunas stand on lakeshores and among trees, so after the heat you cool down in the lake or simply sit outside in the forest air. Most are rented to one group at a time, so you have the sauna to yourselves, but you need to book a time slot ahead. Several are deep in the countryside, so check how you will get there before booking.
A private sauna hut stands on the shore of Lake Shikotsu in Hokkaido, a deep, clear lake ringed by old forest about an hour's drive from Sapporo. Between rounds, steep steps lead down to the lake for a cold dip, and the 150-minute slot also includes a soak in this old inn's hot spring. It must be booked online by the day before.
In a log cabin in the woods beside Lake Nojiri, in the mountains of northern Nagano, a wood-burning stove heats this Finnish-style sauna. The cold plunge is filled with spring water from nearby Mount Kurohime, and in the daytime you can also wade into the lake right in front. Every session is by reservation only.
Lake Shijiori is a small lake hidden in the hills of Yamanashi, and this tent sauna is set up right on its shore at a campground. Step out of the heat into the cool lake, then rest on the shore in the open air. It is rented to one group at a time and must be booked by 5 pm the day before.
This campground sits on the quiet shore of Lake Saiko, one of the Fuji Five Lakes at the foot of Mount Fuji, and its sauna stands close enough to the water to walk straight into the lake. It takes only a few bookings and details are hard to find online, so contact the campground before planning a visit.
A tent sauna on the shore of Lake Shiromaru, a narrow lake in the wooded valleys of Okutama at Tokyo's western edge, where you can cool off in the lake or in the open air beside it. It is one of the few places within Tokyo where the lake serves as your cold plunge. It is a walk from Shiromaru Station on the JR Ome Line, a small unstaffed station with no shops nearby, so bring water and snacks.