A firewood sauna is a type of traditional Finnish sauna that uses wood as the main source of heat. In a firewood sauna, a wood-burning stove, typically made of stones, is used to heat the room. The stove is fueled by wood, which is usually added to the stove through a small door located on the side of the stove.

The heat from the stove warms the stones, which then radiate heat into the sauna room. The temperature in a firewood sauna can reach up to 80-100°C (176-212°F), which creates a dry, hot environment that promotes sweating and relaxation.

Firewood saunas are popular in Finland and other northern European countries, and they are often found in private homes, summer cottages, and public sauna facilities. They are usually constructed using wood and have a rustic, traditional appearance.

Using a firewood sauna can have many health benefits, including improved circulation, detoxification, and relaxation. It can also be a social activity, as it is common for people to go to the sauna together and socialize while enjoying the heat.

Overall, the firewood sauna is a popular and traditional way to relax and unwind in many parts of the world, particularly in northern Europe.