In the German city of Bad Staffelstein, a manmade “cave” of sorts beckons leisure-seekers to a thermal bath fed by Bavaria’s hottest and most powerful saltwater spring. Obermaintherme is a 15,000-square-meter (161,500-square-foot) bath hall whose pool previously boasted a natural-stone cave feature with artificial palms for decades. But in recent years, the saltwater pool and other parts of the facility required upgrades.
All images courtesy LUCEM GmbH
Krieger Architekten Ingenieure took this opportunity to reenvision the grotto-like setting for bathers. Instead of a dated faux cave mimicking natural landscapes, the architects conceived a modernized structure that would still function as a cave by enclosing a portion of the pool to provide a semi-private sensory experience. But additionally, it would become a visual symbol for the center — a luminous salt crystal that seems to jut out of the water.
The new cave is largely constructed with LUCEM, a concrete material that can closely resemble solid stone slabs. But at the click of a mouse or tap on a smartphone, color LED lighting transmits through the panels’ thousands of embedded fiber optics to reveal LUCEM’s translucency. In order to achieve this in a high salt-content environment (that contains almost as much salt as actual seawater), the engineers at Krieger devised a marine-grade steel framing system that was galvanized and coated for corrosion resistance.
After careful study and 3D modeling of all the joints, assembly parts and anchors, the welded frame was installed on a concrete foundation. The project team used double-sided RGB LED modules to illuminate both interior and exterior faces of the cave structure. Between the LEDs and 20-millimeter LUCEM panels on both sides are 2-centimeter-thick transparent polycarbonate spacers that help reduce some of the shadow cast by the structure’s frame. Finally, stainless steel profiles along with flexible silicone seal were applied around each panel of the interior shell.
Computer software activates and controls the lighting, programming the scenario and color scheme as desired or setting it to synchronize with music being played in the hall to give bathers both inside and outside of the new cave a truly unique sensory experience.