The official archives of the Finnish Defense Forces are home to thousands of photos taken during the Finnish WWII era. We’ve highlighted some particularly striking color photos of Finnish soldiers from their collection before, but this time, we thought we’d feature something that remains an icon of Finnish culture: the sauna.

In Finland, which remained a poor and rugged place until post-war industrialization, the sauna played a central part in society. Not only were they were important in maintaining personal hygiene in the dark times before showers, but life often began and ended in the sauna. Childbirths took place in their cleanly environments, and the deceased were sometimes prepared for burial in them. Finns have been socializing, cleaning, and even cooking in saunas for centuries, so it’s easy to see why the sauna is such a huge part of Finnish culture even today.

Naturally, Finnish soldiers during the WWII era needed access to the sauna. Soldiers were known to light up any usable sauna they happened across in the field. When there were no usable saunas in sight, the soldiers would do what any sensible Finn would do—they built their own sauna. Sometimes using logs, and sometimes using only the terrain, Finnish soldiers could have a working sauna up and smoking in a matter of hours. In order not to give away their position with tell-tale sauna smoke, Finnish soldiers on the front lines would usually only light it up at night, getting in and out as quickly as possible. Soldiers in more remote locations had the luxury of enjoying their steams a bit longer.

We could go on and on about the wonders of the sauna, but don’t just take our word for it. Take a look at these amazing photos with translations of the original Finnish captions. They depict the Finnish soldiers of WWII who built and used saunas, even during wartime—one drop of sweat at a time.