Tor Alva Unveiled: From Confectioners to Robots

The usually sleepy Mulegns was a hive of activity on this spring day, with visitors coming from all over Switzerland and from further afield to see the white tower for themselves for the first time. The cover was only removed by helicopter on the eve of the opening, revealing the delicate, white structure, which now blends into the mountain landscape of the Julier Pass.

Tor Alva is a new architectural landmark and a pioneering work of digital fabrication that is intended to revive Mulegns, a mountain village threatened by depopulation that is currently home to 11 people. The Origen cultural foundation led the work in collaboration with ETH Zurich, to celebrate culture and the arts and to give the village a new lease of life. Starting 23 May, 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 re-erected elsewhere.

Digital craftsmanship

The form of 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 up over four storeys, becoming thinner and more branched, before fanning out in an almost tree-like fashion to form the domed space at the top.

The 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.

New concrete, new technology

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.

Two robots working hand in hand

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 centimetres. 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 which 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 future be tested just as safely as conventional reinforced concrete structures.

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 (Read more in this report ).

Views on the opening

The opening ceremony brought together project partners, public officials and distinguished guests from the realms of science, politics and the arts - all united in their recognition of the tower's symbolic and technical significance.

President of ETH Zurich Joël Mesot sees the structure as a symbol of collaboration between the science community and industry: "The tower combines the latest insights from research with the expertise of companies and experts. Building the tower here, at the foot of the Julier Pass, has also allowed our researchers to gain important practical experience."

Giovanni Netzer, theatre director and founder of the Origen cultural foundation, described the project as a compelling synthesis of technology and artistic intent. "I was fascinated by the interplay between digital design, traditional craftsmanship, cultural memory and artistic form," he said. "The White Tower is more than a technical triumph - it inspires the building sector, encourages sustainable tourism and offers new cultural space. It also gives a fading village a new chance. That's extraordinary."

In his welcome address, Federal Councillor Guy Parmelin praised the broad cooperation that had brought the vision to life. "The 3D-printed White Tower recalls the legacy of the Graubünden confectioners while showcasing innovation and collaboration," he said. "Novel ideas and technical know-how from ETH Zurich, the visionary drive of the Origen cultural foundation and support from public authorities, companies and private individuals made this exceptional project possible. I'm convinced this will become a cultural and touristic landmark."