Friend Trig is a keen outdoors swimmer. Once the sea hits 14 degrees C (57 F) he goes regularly for pretty long swims with some equally rugged amphibious friends.
For his birthday, his swimming buddies gave him a mobile sauna (above). They found an old camper, fitted it with paneling and a small sheet metal wood stove. No nails can be exposed in the interiors of saunas, you need to conceal them or use wooden pegs instead. (It's a comfort issue. Exposed nails would burn all that exposed flesh.) Together with all the curves and rounded corners, this makes for some pretty challenging carpentry.
I tried getting some decent pictures of the interior (below) but guests at Trig's birthday party kept running in and out in various states of undress. As a guy who's too touchy to publish people's real names I'm not going to start posting pictures of them in the nude.
The whole thing weighs around 300 kilos (660 lbs), so it can be dragged some distance by hand. In this case, three guys pulled it a kilometer (0.6 miles) along a restricted access road.
Allow me to recommend the Finnish movie Steam of Life, a documentary about Finnish men who talk about serious, personal stuff while in various saunas. The people in the film are entirely nude almost the whole time. This is a non-issue for Finns. But the directors started worrying when they came to the US to show it, and saw how a reality show on tv that involved milking a cow had blurred out the cow's udder. It all went well, however.
Steam of Life, trailer, above. Note the phone booth-sauna and the old thresher-sauna. Much like stoners see any container as a potential bong, Finns see any structure as a potential sauna.