The RIBA has named its four finalists for the 2026 International Prize, the award it describes as recognizing the best new building in the world. Among them is the transformation of Royale Belge in Brussels by Caruso St John Architects, working with Bovenbouw Architectuur and DDS+.
The shortlist was drawn from the 34 projects that received RIBA International Awards for Excellence earlier in the year. The winner will be announced on 15 October 2026 at the Stirling Prize event in London. The International Prize is given to a building that demonstrates visionary thinking and design excellence while making a clear contribution to its users and its physical context.
A Modernist landmark given new life
Royale Belge stands in Watermael-Boitsfort, in the south-east of Brussels, surrounded by forest. Originally designed in the 1960s by Belgian architects René Stapels and Pierre Dufau as the headquarters of an insurance company, the cross-shaped office tower is a recognizable Modernist landmark. After decades of corporate use it faced the familiar questions that confront many large postwar buildings: how to keep the structure, improve its performance, and give it a role that serves the city rather than a single company.
Caruso St John, together with Bovenbouw Architectuur and DDS+, approached the project as a careful act of adaptive reuse. The existing frame and character of the building were retained and protected. New programmes were introduced, including restaurant, hotel and gym uses, turning the former headquarters into a mixed-use hub. The work demonstrates how a 50-year-old commercial tower can be extended in life and purpose without being erased or heavily disguised.
The RIBA citation highlights the project’s location among the trees and its successful transition from single-tenant office to a more public and varied building. In a period when the environmental and cultural cost of demolition is increasingly scrutinized, Royale Belge stands as a substantial example of what can be achieved by working with what already exists.
Why the shortlist matters
The 2026 International Prize shortlist is deliberately compact. Only four projects advanced from the wider field of Award for Excellence winners. The presence of Royale Belge places a major European retrofit in direct conversation with other works that address climate, resource use, social need and urban change. Two of the four finalists are in Belgium, underlining the strength of recent architecture in that country.
For Caruso St John the nomination continues a long engagement with existing buildings. The practice has repeatedly shown that careful transformation can produce architecture of high quality and lasting public value. Royale Belge joins a body of work that treats the given structure as a starting point rather than an obstacle.
Adaptive reuse as contemporary practice
The project’s significance lies partly in its scale and partly in its attitude. Large Modernist office buildings are often seen as difficult to adapt. Their deep plans, specialized services and corporate image can resist new uses. Royale Belge shows that with rigorous analysis, precise intervention and a clear programme, such buildings can be brought into a new phase of usefulness.
The collaboration between a British practice and Belgian partners also reflects the collaborative reality of complex reuse projects. Local knowledge of regulations, construction culture and the specific history of the building is combined with an external eye that can reframe what the structure might become.
Computational tools and detailed survey work are essential in this kind of project. Understanding the existing structure, its tolerances, its thermal behaviour and its potential for new servicing requires accurate digital models. Decisions about what to keep, what to upgrade and what to insert are tested against performance, cost and heritage value. The final architecture appears calm and resolved, yet it rests on extensive analysis of the given fabric.
Looking toward October
The RIBA International Prize has previously recognized projects that combine design quality with social or environmental ambition. Royale Belge enters the final stage as a strong representative of adaptive reuse at a substantial scale. Whether or not it takes the ultimate award, its presence on the shortlist confirms that transforming an existing landmark can stand alongside new construction as a form of architectural excellence.
The jury will visit the shortlisted buildings before making its decision. On 15 October the winner will be named. Until then, Royale Belge stands as a clear statement: the best new building in the world might already be standing, waiting to be carefully reimagined.
