The sauna was created by Modulorbeat for an annual arts festival called The Detroit Project, which encourages local creatives to develop practical and artistic projects in response to the area's changing employment situation.
The region was historically the site of many major coal and steel mines that have gradually closed, while car manufacturer Opel's factory in Bochum is scheduled to cease production later this year.
As part of a project called Borderlands, which examined the use of spaces on the fringes of Bochum, the architects proposed a sauna located on the site of an abandoned factory.
"Our idea was to transform a former industrial site into a sauna, which is connected to the idea of doing nothing," architect Jan Kampshoff told Dezeen. "People working in the mines or the factories receive healthcare and leisure time so when these companies disappear they need other ways to look after themselves. That's why we made a sauna."
The project team developed the idea of a vertical shaft as an inverted representation of what is hidden below ground throughout the region.
Cast concrete components ordered from the catalogue of a mining supplies firm are stacked to create a hollow structure that is separated into three distinct functional zones.
"The organisation of the different areas represents a methodical process, like working in a factory," Kampshoff added. "We thought the ritual of taking a sauna is connected to idea of how work is organised."
A ladder of metal treads is embedded in the outer wall of the base section and leads inside the cantilevered volume perched above.
This central section houses the electrically-heated sauna, which is contained in a wooden shell with a transparent plastic roof enabling daylight to reach the interior.
The ladder continues to the upper level, where a metal grille platform and bench create a relaxation area.
A translucent roof can be opened to provide views of the sky and allows the user to poke their head out to overlook the surrounding landscape.
The bottom level is made from a standard waterproofed concrete shaft section, which is normally used to keep water out but has instead been filled and used as a plunge pool.
Narrow gaps between the concrete sections allow light to filter through and permit glimpses of the natural surroundings.
The sauna is open at weekends until 5 July and can be reserved on the project's website. At the end of the festival it will be dismantled and moved to a new location.
Modulorbeat is a collective comprising architects, urbanists and designers based in the German city of Münster. Its previous projects include a golden pavilion constructed in Münster's market square to house an exhibition on local Medieval goldsmiths.
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