for the Federal Office of Sports (OFCL) site. The chosen heat source being geothermal energy on a scale new to Switzerland, the project had to be innovative and sustainable, with a view to becoming a landmark in both technical and architectural terms. The layout and construction methods must also be resource-efficient, using ecological and recyclable building materials. Taking these elements into account, the “Luciole” project (firefly in french) is conceived as an iconic building, which is both a point of reference for the area and a facility with technical, environmental and social benefits. Prominently positioned in the Biel landscape, the power plant also serves as a place for sports and contemplation. The ambition of the “Luciole” is to make an energy-producing building not a burden, but a facility that contributes to the life of the place. The power station’s technical rooms have been stacked to create a vertical volume, a lantern raised into the sky, which stands out against the distant backdrop. At its top, an observation terrace accessible to all adds to the appeal of an infrastructure that is usually closed to the public.