In 1991, Ernst Beyeler addressed Renzo Piano to commission the design of a museum to accommodate his outstanding collection of modern art. Beyeler's request is a museum entirely illuminated by natural light and surrounded by greenery. The building has a very strict plan: four masters of the same length, oriented in the north-south direction, run parallel to the wall of the enclosure and neatly mark the succession of the exhibition spaces that originate from the central atrium. Natural light penetrates through the filtering surfaces of the roofing system that "flies" above the walls. The roof is somewhat independent of the building: supported by the metal structure, it extends far beyond the perimeter defined by the walls.