My folks have a barrel sauna up at our camp. It’s really a huge cedar barrel, made by Superior Cooperage out of Minnesota. It’s a lovely piece of work, but if you’re thinking of ordering one from them, be aware that it may take a while for it to arrive.
Standard Sauna Procedure is to use a stove covered in rocks to heat a cedar-paneled room to around 200 degrees Fahrenheit, then add steam to the atmosphere by pouring a ladle or two water over the hot rocks. Once everything is hot and humid, you should bask in the room for about fifteen minutes, then go jump in either the snow or a cold freshwater lake, whichever you have handy.
Standard procedure needed to be altered a bit for camp. The sauna is separated from Lake Superior by a ridge of rather treacherous chunks of sandstone. Anyone running from one to the other would likely wind up with a few broken or sprained ankles, knees and possibly wrists and elbows. And, despite rumors to the contrary, snow becomes difficult to find in some summer months.
Instead, there’s an outdoor shower set up next to the sauna. Basically it’s an old whiskey barrel with a shower head on the bottom. The water in the barrel is warmer than the lake, but still cool enough to be a nicely bracing wakeup after you’ve been sweating for a quarter hour.