Located in the Värmdö municipality, Sauna R has been dug into a shallow slope, accessed via a thin path that winds through the rocky surroundings dotted with cabins.
The simple box faces northwards towards the sea.
A full-height, sliding glass door provides views out over the water, which can be enjoyed from a monolithic stone bench in the sauna room.
"The space is like a camera obscura, a little box drawn to shape the views of the landscape," said Foresti.
Internally, large slabs of polished Negresco Quartzite have been used to line both the floors and the walls, creating a monochrome space given texture by the stone's white veins.
A thin glass partition and door can divide the sauna space into two, separating the area with the kitchenette from the sauna stove and stone bench.
Dug into the hillside at the rear of Sauna R is a secondary space with a shower and toilet.
Sliding, dark wood doors conceal the entrance to these facilities, blending in with the rest of the interior when not in use.
Dramatically lit by a skylight, the narrow bathroom has also been finished in all-black, including the fixings, sink and toilet.
The stone flooring of the interior extends out to create a small terrace in front of the structure, making a space for sitting and taking in the view and fresh air.
On top of the sauna roof another terrace is an additional space for overlooking the landscape.
Bringing in light during the day, the sauna's large window turns the structure into a beacon at night.
The interior can be illuminated by a concealed strip of lighting at the rear of the space.
Matteo Foresti studied architecture in Italy prior to moving to Stockholm and founding his practice in 2017.
Also in Sweden, Milan-based practice Small Architecture Workshop designed a charred-wood sauna floating on a lake in Åmot, overlooking the water through a large window.
An Egg-shaped sauna was also designed for the residents of the Swedish town of Kiruna by Bigert & Bergström.
Photography is by João Morgado.
Architect: Matteo Foresti
Construction company: Lindblad&partners
Landscape architect: Torsten Wallin – WSP
Engineer: KE gruppen
Carpenter: Jiwes Modell & Snickeri
Ventilation: DC vent
Plumber: Ericsson & Holmstedt
El: Pernolds El
Stone floor and walls: Negresco quartzite with leather finishing and matt finishing
Sauna heater: Sentiotec – Concept R 2.
Bathroom accessories: Dornbracht Supernova
Bathroom sink: Alape