The traditional Finnish sauna is a water/energy phenomenon. By using wood (traditionally) or rocks to heat volcanic rocks, water can be splashed on the rocks to create steam. This steam is naturally circulated around the sauna, especially if you’re fortunate enough to be in a barrel sauna.
The sauna is the perfect representation of heat/energy and water. When in a wood-burning barrel sauna you can feel it in your core. You can see it, hear it, and it will relax you immensely.
The barrel sauna is also a lesson in off-grid heating. The sauna stoves are efficient, effective, and cheap.