The history of sauna.

Bathing in heated air is older than written history. Archaeological evidence places ritual sweat structures across Eurasia and the Americas as far back as the Mesolithic, hot stones laid in pits, water poured over them to create a hot, steam-saturated cavity. The mechanism that defines a sauna today (radiant heat plus löyly, the steam burst from water on hot stones) was already complete.

Independent versions of the same idea appear in early Native American sweat lodges (inípi in Lakota culture), pre-Roman Celtic sweat houses (Irish teach an alais), Mesoamerican temazcal, and across Northern Eurasia.

By the Iron Age, settlers across what is now Finland had refined the sweat pit into a dedicated wooden structure: the savusauna, or smoke sauna. A large pile of stones was heated for hours by an open fire, the smoke filling and blackening the room. Once hot, the fire was extinguished, the smoke vented, and the sauna used over several hours as the stones held heat.

Almost every Finnish family had one. It was the warmest, cleanest space in the settlement, used not just for bathing, but for childbirth, for laying out the dead, for smoking meat, and for negotiating the most serious matters. The sauna's role as a sacred secular space, somewhere you arrive honestly, equal, undefended, was established here.

Rome industrialised the sauna idea on a scale that has rarely been matched since. The thermae were enormous public bathing complexes, the Baths of Caracalla covered 13 hectares and could hold 1,600 bathers, running a sequence of rooms from cold (frigidarium) through warm (tepidarium) to hot (caldarium) and sometimes a final dry-heat sweat room (laconicum).

The thermae were free or near-free, open to every social class, and powered by hypocaust heating, hot air channelled under raised floors. They were the original wellness infrastructure: bathing was understood as health, social cohesion and physical preparation in equal measure.

While the Roman model declined with the Empire, the practice continued and evolved. The Russian banya, wood-fired, very hot, often with birch venik branches used to massage and stimulate the skin, became the central health practice of rural Russia and remains so. Medieval Western Europe had thousands of public bath-houses, the German Schwitzbad, until the Black Death triggered widespread closures and a 400-year retreat from public bathing.

Across the Islamic world, the Turkish hammam evolved from the Roman thermae, keeping the cold-warm-hot sequence but adding the marble göbektaşı (warm belly stone) for prolonged sweating and tellak attendants for scrubbing and soaping.

Japan's sentō public bathhouses date back at least to the Heian period (794–1185), but the Edo period industrialised them across cities. Initially focused on hot water immersion, the sentō tradition evolved alongside dry-heat sauna rooms in larger facilities, and the cultural attitude, clean before you enter, sit quietly, be present, informs the modern Japanese sauna boom of the 21st century.

Across Western Europe, public bathing collapsed for four centuries: a combination of plague, Reformation-era moralism, and the rise of cheap soap and private washing reduced the cultural status of communal sweating to almost zero. The Finnish countryside was one of the few places where the practice continued essentially unbroken. A Finnish proverb dating to the period: saunassa ollaan kuin kirkossa, “in the sauna, one behaves as in church”.

It is largely thanks to Finnish stubbornness, and the sauna's tight integration into Finnish identity, language and home design, that the practice survived to be reintroduced to the rest of the world in the 20th century.

The 1936 Berlin Olympics is the moment the modern world saw the Finnish sauna up close. Finland's runners brought their own portable sauna and used it for recovery; international press took notice. Twenty years later, at the 1952 Helsinki Olympics, Finland presented sauna as a national gift, and the export began in earnest.

The electric sauna stove, patented in Finland in the 1930s and refined by Metos and Helo through the 1950s and 1960s, removed the firewood and smoke from the equation and allowed sauna to scale into hotels, gyms, homes and offices around the world.

Infrared heating, using long-wavelength infrared radiation to warm the body directly rather than heating the room first, was first commercialised for medical and physiotherapy use in Japan and the United States in the 1960s. The first dedicated infrared sauna cabins for home use emerged in the 1990s, marketed initially to athletes and people who couldn't tolerate the high air temperatures of a traditional sauna.

Far-infrared (FIR) became the consumer default. More recent full-spectrum cabins (combining near, mid and far infrared) are designed to provide the deeper-tissue penetration of NIR alongside the broader sweat response of FIR. Both work via different mechanisms to Finnish sauna and arguably represent the first genuine evolution of the form in 2,000 years.

Three things converged in the 2010s to push sauna into the longevity mainstream: the Finnish KIHD cohort studies (Laukkanen, University of Eastern Finland) producing the strongest mortality and cardiovascular evidence base any single intervention has ever generated; the rise of biohacking and longevity podcasts (Rhonda Patrick, Andrew Huberman, Peter Attia) translating that science for a non-academic audience; and the practical infrastructure to deliver high-quality sauna at scale outside Finland.

By 2024, sauna had moved decisively from spa-day indulgence to core recovery and longevity tool. Bryan Johnson's Blueprint protocol, daily 20-minute sauna sessions as part of his stated effort to reverse biological age, pushed the practice further into the cultural foreground. R1SE Sheffield was built into this wave.