Blue21’s Square Floating City: Scaling floating urban development for coastal resilience

The company designs, researches and builds floating projects in delta and coastal cities worldwide. Blue21’s work is grounded in the conviction that cities should move beyond simply sustaining existing systems towards actively restoring urban and ecological balance. Floating development, in their view, is not only an engineering solution but a way to create space for new ecosystems, bio-based economies and climate-adaptive urban living.

From individual projects to a scalable urban concept

Blue21 gained international recognition through pioneering projects such as Rotterdam’s Floating Pavilion. The Floating Pavilion was built in a tidal harbour with direct exposure to open sea conditions. This and other early projects demonstrated that large-scale floating structures can operate safely and effectively under dynamic conditions such as tidal movement and wave action. They also showed that floating buildings can add architectural quality and public value to waterfront areas.

Building on this experience, Blue21 established a dedicated entity: Square Floating City. While Blue21 continues to work on different scales of floating solutions, Square Floating City focuses specifically on large-scale floating urban development, extending well beyond individual buildings. The aim is to create floating neighbourhoods and districts that function as integrated, liveable parts of the city.

Modular, resilient and ready to implement

The Square Floating City approach centres around a carefully engineered modular system. Floating neighbourhoods are composed of standardised modules that can be combined into clusters, districts or even entire floating cities. This modular logic allows cities to phase development, respond to changing demand and reduce long-term investment risk in uncertain climate conditions.

The size and configuration of each module are defined by local physical parameters such as water depth, wave climate, tidal range and wind exposure. These conditions determine structural design, mooring systems and platform dimensions, and ensure robustness and safety in diverse coastal settings. At the same time, social resilience is a key design principle. A single neighbourhood module typically accommodates around 110 to 130 residents. This is exactly the scale associated with strong social cohesion and community resilience. 

Utilities and infrastructure are embedded in the floating platforms and include energy systems, water services and mobility solutions. The platforms can accommodate shared vehicles, neighbourhood batteries and technical installations below deck. This reduces the visual impact while increasing robustness during extreme events. Looking ahead, floating districts may also integrate urban food systems, including ocean-based production, as part of a broader urban ecosystem. 

A new planning logic for coastal cities

Floating urban development introduces a fundamentally different planning logic. Floating modules move with water levels, allowing them to adapt to sea level rise without constant physical modification. Their mobility also offers strategic flexibility: modules can be constructed at dedicated locations, towed to their destination, and, if needed, be relocated as urban priorities evolve.

To support cities identify suitable locations, Square Floating City has developed a global city scan that analyses physical, spatial and economic criteria. This tool highlights coastal cities where floating neighbourhoods could add significant value. Cities such as Wellington, Melbourne and Sydney rank highly in these assessments. Their locations reflect a combination of extensive waterfront areas, strong urban growth pressure and increasing exposure to climate-related risks.

Living with water as an urban strategy

The work of Blue21 and Square Floating City highlights a broader shift in thinking about water and cities. Rather than resisting water, floating urbanism embraces it as an asset. For coastal cities facing long-term uncertainty, floating neighbourhoods offer a realistic and scalable pathway to expand housing supply, strengthen climate resilience and enhance urban quality.

By combining Dutch water expertise with local knowledge and international research, Blue21 and Square Floating City demonstrate how floating development can move from experimental projects to a mature component of urban planning. As climate pressures intensify, learning to live with water may become one of the defining challenges – and opportunities – for coastal cities worldwide.