The Six Guardians: Sustainable Bridge Architecture for a Greener Copenhagen

The Six Guardians is a visionary example of sustainable bridge architecture that redefines infrastructure as an active public landscape. Conceived as an ensemble of small-scale public spaces, the project transforms a conventional urban crossing into a green civic experience that supports mobility, ecology, and social interaction. Designed for Copenhagen, the proposal responds directly to the city’s ambition to become carbon neutral while strengthening its identity as a global leader in cycling infrastructure and environmentally responsible urban design.

Developed by Susan Hoekstra and Roman Birrer, The Six Guardians was a Shortlisted Entry of The City Link competition, proposing a bridge that does far more than connect two riverbanks. Instead, it introduces a sequence of inhabitable structures that invite residents and visitors to slow down, pause, and engage with nature in the heart of the city.

Perspective view of The Six Guardians, integrating cycling lanes and elevated green platforms across Copenhagen’s waterfront.

Aerial site plan showing the bridge’s connection between urban blocks and existing cycling infrastructure.

Sustainable Bridge Architecture as Urban Landscape

Rather than treating the bridge as a single linear object, The Six Guardians is composed of eight delicate architectural elements. Two floating platforms are positioned at the center of the river, while six inverted octagonal pyramids—three on each side—anchor the structure to the urban edges. These pyramidal forms rise from minimal structural footprints, reducing contact with the water and limiting disruption to the aquatic ecosystem.

Each element functions as a small public garden, planted with Scandinavian montane birch trees. Together, these planted platforms form a continuous green corridor that visually and ecologically extends Copenhagen’s existing cycle routes across the water. The result is a bridge that operates simultaneously as infrastructure, park, and environmental intervention—an exemplary model of sustainable bridge architecture integrated into the urban fabric.

Cycling, Walking, and Multi-Level Public Use

The bridge is carefully organized into multiple levels, each dedicated to a specific mode of movement or activity. Cycling routes follow a clear and efficient one-way system, allowing riders to cross the river without interruption. At the same time, pedestrians are guided through a slower, more intimate pathway that meanders between planted platforms and seating areas.

At the center, the floating platforms introduce flexibility into the structure. These elements can open to allow boat passage, maintaining Copenhagen’s active waterways, while also providing generous waiting spaces for cyclists. Integrated programs such as a bicycle repair station, rental point, kiosk, podium, and small tribune transform the crossing into a destination rather than a transitional space.

Section and structural diagram illustrating floating platforms and minimal contact with the water ecosystem.

Pedestrian experience within the planted bridge landscape, offering rest, shade, and city views.

Environmental Strategy and Ecological Sensitivity

Sustainable bridge architecture lies at the core of The Six Guardians. The lightweight structural system minimizes material use and reduces the impact on sensitive aquatic environments. By limiting foundations in the water and elevating green spaces above the river, the design protects marine life while introducing new habitats within the city.

The planted pyramids contribute to Copenhagen’s broader environmental goals, including ambitious targets for carbon reduction and urban tree planting. These green interventions improve microclimate conditions, enhance biodiversity, and offer residents direct contact with nature during everyday commutes.

A Bridge Designed for People

Beyond environmental performance, The Six Guardians emphasizes the human scale. The project acknowledges that successful urban infrastructure must encourage participation and social interaction. Seating areas, shaded platforms, and scenic viewpoints invite people to stop, meet, and observe city life from a new perspective.

By combining mobility with leisure and ecology, the bridge becomes a shared civic space—one that supports families, cyclists, pedestrians, and visitors alike. This human-centered approach reinforces the idea that sustainable bridge architecture can actively shape healthier, more inclusive cities.

The Six Guardians demonstrates how sustainable bridge architecture can transcend technical function to become a catalyst for urban transformation. By merging cycling infrastructure, public space, and ecological design, the project offers a compelling vision for future city links—where bridges are not just crossings, but living landscapes that connect people, nature, and the city.