Designed to blend in with the pitched rooflines of the surrounding rural structures the pool was built as part of an upgrade of a former 1980s water park by Ljubljana-based studio Enota.
Named Termalija Family Wellness, the pool is the latest in a series of developments at the spa with the overarching aim of better connecting the centre with the surrounding natural landscape.
The new pool replaces an outdoor pool on the site that had been fitted with a retractable membrane cover to allow for use in winter in summer and winter, but had proven too complex to ever be used in practice.
While previous developments to the complex were largely underground, illuminated by cylindrical skylights and drawing on the undulating green landscape, the enclosure of the pool required a large intervention above ground.
"No longer being able to reference only the surrounding natural landscape, the solution was found in the scale and form of the surrounding vernacular structures," said the studio.
Accessed via a series of paved paths that dig down into the landscape, the centre is wrapped in glazed walls that maximise the amount of light entering the pool space.
"The large roof above the water area was divided into sets of smaller segments to prevent its scale from overwhelming the surroundings," explained the studio.
"Viewed from a distance, the shape, colour and scale of the new clustered structure of tetrahedral volumes is a continuation of the cluster of surrounding rural buildings, which visually extends into the heart of the complex."
Inside, the faceted geometry of the roof scape creates a dynamic, wood-clad ceiling structure, illuminated by skylights at the apex of the roof sections and supplemented by artificial lighting.
The geometry of the roof also allowed for the span of the roof to be achieved with minimal structural supports, minimising disruption to the pool below and further contributing to a feeling of openness and lightness.
The pool itself has been finished with sculptural concrete forms that double as containers for plants and trees, creating a space with the feel of an open, outdoor area during summer and a closed area during winter.
"Despite its size and the space it occupies, the new roof simply acts as a big summertime sunshade and does not usurp the precious exterior space," explained the studio.
Enota's previous projects have a similar focus on merging architecture and landscape, including a sculptural promenade along a waterway in the city of Velenje and two sloping concrete volumes enclosing an open-air chapel in Skorba.
Photography is by Miran Kambič.