The world’s tallest 3D-printed tower, known as Tor Alva (meaning “White Tower” in Romansh), was inaugurated in Mulegns, Switzerland. The building showcases how digital construction techniques can be used to build load-bearing structures without formwork. It is an initiative of the Origen cultural foundation (Nova Fundaziun Origen) in collaboration with ETH Zurich, and is designed to serve as a cultural hub and to breathe life into a village threatened by depopulation. Starting May 23, 2025, the White Tower will be open daily for guided tours. From July onwards, the space will also host staged performances. Tor Alva is intended to remain in Mulegns for around five years. It can later be dismantled and reerected elsewhere.
The Tor Alva has four levels, each with eight reinforced 3D-printed concrete columns. Image: Birdviewpicture/Nova Fundaziun Origen
The structure is reminiscent of an ornate layered cake — a reference to the emigration history of confectioners from Graubünden who exported their skills from here to the whole of Europe. Thirty-two sculptured white concrete columns rise over four stories, becoming thinner and more branched, before fanning out in an almost tree-like fashion to form the domed space at the top.
The Tor Alva tower was designed by architect Michael Hansmeyer and ETH Professor of Digital Building Technologies Benjamin Dillenburger. Instead of relying on traditional concrete formwork, they opted for an additive manufacturing process, whereby an industrial robot applies the concrete layer by layer into free-form elements without any supportive casting moulds. The design is based on complex algorithms that generate the ornamental and the structural aspects at the same time.
ETH professor Benjamin Dillenburger (left) together with researchers Ana Anton, Che Wei Lin and Timothy Wangler in ETH Zurich’s Robotic Fabrication Lab. Image: Michele Limina/NZZ
To make this process possible, a specially developed concrete was needed. It had to be soft enough to bond the delicate structures, while hardening quickly enough to support the subsequent layers. Robert Flatt, ETH Professor of Physical Chemistry of Building Materials, developed a novel mixture for this purpose. Just before the concrete leaves the pressurized nozzle, two additives are blended into the mixture, allowing the characteristic droplet-like relief on the columns to be achieved.
ETH professor Robert Flatt developed a new type of concrete mix for the 3D printing of the column elements. Image: Ana Anton/ETH Zurich
What is special about this project is that the 3D-printed elements not only serve as a shell, but for the first time, they are also load-bearing. Until now, a suitable method to reinforce 3D-printed concrete effectively has been lacking. This is now possible thanks to a newly developed reinforcement concept implemented using a robot-assisted innovation. While one robot applies the concrete in layers, a second places a ring-shaped reinforcement in the new structure every 20 cm. This horizontal reinforcement in the form of rings is supplemented by longitudinal rebars that are added after printing. The process, known as “reinforcement that grows,” was developed by ETH professors Walter Kaufmann, Robert Flatt, and Benjamin Dillenburger, in conjunction with the ETH spin-off Mesh and the company Zindel United. In addition, the researchers developed a new testing method that allows the load-bearing capacity of 3D-printed concrete to be reliably calculated for the first time. This is a key requirement to ensure that such buildings can, in the future, be tested just as safely as conventional reinforced concrete structures.
The Tor Alva has a double dome consisting of 32 branching columns. Image: Benjamin Hofer/Nova Fundaziun Origen
It took five months to print the columns on the ETH Hönggerberg campus. The components were then assembled in Savognin and delivered to Mulegns via the Julier road in a heavy goods vehicle (as discussed in this report).
To read the complete story and learn more about the project, visit ethz.ch/en/news-and-events/eth-news/news/2025/05/from-confectioners-to-robots-tor-alva-in-mulegns-is-unveiled.html.
Filed Under: 3D printing • additive • stereolithography
