ETH Zurich and ROK Architects have developed a lightweight, reusable concrete spiral staircase installed in the STEP2 Unit of the NEST research building in Dübendorf, Switzerland. The Cadenza staircase consists of 16 identical prefabricated steps cast from a single reusable 3D-printed formwork, significantly reducing material waste associated with conventional concrete production. Each step is only 20 mm thick and made from ultra-high-strength, steel fiber–reinforced concrete, resulting in eleme