Greening of Flagey and Sainte-Croix Squares – Brussels by Kollektif landscape
Belgium / Built in 2025 /
kollektif.be
Greening of Flagey and Sainte-Croix Squares – Brussels
This project concerns the greening of Flagey Square in Brussels, a vibrant urban hotspot at the foot of the iconic National Institute for Radio Broadcasting (NIR) building. In 2007, Latz & Partners transformed the square — built above an underground car park and stormwater basin — into a exemplary landscape project, characterised by a uniform blue stone surface, a long red urban bench, and playful fountains. Just fifteen years later, changing climatic conditions urge us to add a new green layer to the square, responding to contemporary urban challenges related to heat, water, and biodiversity. In collaboration with the Bouwmeester Master Architect (BMA) a design competition was launched in the summer of 2021.
The winning proposal by Kollektif and Fallow introduces a subtle green transformation of the two squares, remaining true to the original design’s key principles. The central open space — a reference to the former ponds of the Maalbeek valley — is preserved. Greening and de-paving interventions are placed in the peripheral zones, around existing trees and seating areas. This creates a more intimate, human-scaled fringe with room for meeting and lingering. The project foresees the removal of approximately 15% of the hard surface, providing 2,000 m² of additional green space, including 60 new trees. These green areas are carefully inserted within a complex urban context, shaped by events programming, underground infrastructure, and circulation requirements.
The design features three types of greening: the planted corridor behind the continuous urban bench, solitary trees marking the entrances to the squares, and ‘garden zones’ with larger, contiguous planting beds that create a sense of intimacy and foster biodiversity. Special attention is paid to native species and ecological value. A layered planting structure — comprising tree, shrub, and herbaceous layers — provides habitat, food, and shelter for urban fauna such as birds, insects, and pollinators. The green corridor behind the bench links both squares ecologically and offers seasonal variation through bloom, texture, and scent. In collaboration with the ecologist from Ecorce, a balance was struck between planting and sowing, allowing for a living and evolving green expression.
Flagey Square is situated in a flood-prone area and faces a genuine water management challenge. As such, sustainable stormwater management formed a core element of the design. The planting zones act as rain gardens, capturing up to 50% of the surface runoff from the squares. Infiltration beds filled with gravel, buffering provisions, and strategically placed overflow zones ensure delayed drainage, reducing pressure on the sewer system. In this way, the square contributes as a sponge within the city’s hydrological network.
The project was developed through dialogue: design proposals were systematically reviewed in consultation with relevant public bodies, event organisers, and local businesses. A complex mapping exercise of all spatial and event-related constraints informed the highly precise delineation of the interventions. A student workshop mapped out user patterns on the square, delivering valuable insights. This participatory approach enabled not only spatial but also social structures to be revealed and integrated into the design.
The greening of Flagey and Sainte-Croix is a subtle yet powerful intervention. Immediately upon completion, the project contributed to a softer, more vibrant appearance of the square, encouraged new spontaneous uses, and delivered direct climatic benefits such as cooling and stormwater buffering. Though modest in its visual language, the interventions result from in-depth design and technical research into their feasibility. In this regard, the project is both relevant and exemplary of the challenges today’s landscape architects face — a landscape gesture that honours the spirit of the original design, while reactivating it in response to the demands of a climate-resilient future.
• Other landscape architecture offices involved in the design of the landscape:
Kollektif landscape – Fallow
• Other credits:
Ecorce (ecology – hydrology)
Jan De Wilde (photography)
