Seriously, you don’t know what sauna is? A sauna is a small room designed to be heated to very high temperatures, with well-controlled humidity. It is used both for recreational and therapeutic purposes, with most people utilizing them as a relaxation tool that provides additional health benefits.
Sauna is very popular in Northern Europe. Especially in Finland, Estonia.. and so.
Here's a funny video about A Estonian Farmer who did drive to store to buy beer with his Sauna that he had invented. His sauna have caterpillar tracks.. and engine. So he can drive anywhere with his sauna. To a lake to swim, or to store to buy more beer. :P