With nearly 90% of the world’s cities located near coastlines, and sea levels projected to rise by up to two metres within the next 80 years, the question of how we build for the future has never been more urgent.

By 2050, most coastal cities will face increased flooding, infrastructure strain, and population displacement. Traditional solutions, like sea walls and flood defences, are already in use: from Shanghai’s 520 km of coastal barriers, to Hamburg’s waterproof architecture, to New York’s seven-mile protective ribbon circling Manhattan.

But with global spending on coastal protection expected to hit $400 billion by 2040, some architects and engineers are asking a different question: instead of fighting the ocean, what if we built on it?

Enter floating cities, an ambitious yet increasingly viable approach to climate-resilient urban development.

In this article, we explore how floating cities work, the pros and cons, the technologies that make them possible, and the real-world projects that are turning this bold vision into reality. We’ll discuss:

• What is a floating city?
• How do floating cities work?
• What are the pros of floating cities?
• What are the cons of floating cities?
• What is an example of a floating city?
• What is seasteading?
• Would it be possible to float an entire city on a big shipyard?
• Why can’t we float an entire city on a shipyard?
• Are artificial islands the answer?
• What’s the real solution to building floating cities?
• What is seament (bio rock) and how does it help construction?
• Could floating cities be a cheaper, more sustainable future?
• When will floating cities become a reality?

First up…

What is a floating city?

A floating city is a type of urban development built on buoyant platforms that sit on the surface of a body of water, typically the ocean. These are not traditional ships or oil rigs but engineered, modular structures designed to support permanent human habitation, including housing, infrastructure, public spaces, and essential services.

The idea behind floating cities is simple yet revolutionary: if rising sea levels threaten coastal communities, why not build our cities on top of the water instead of behind sea walls or on unstable reclaimed land?

Floating cities aim to be self-contained, climate-resilient, and environmentally sustainable, offering an alternative to land-based urban development that may no longer be viable in the face of climate change, population growth, and disappearing coastlines.

How do floating cities work?

Floating cities are built on interconnected buoyant platforms, often made from engineered concrete or advanced materials like seament (bio rock), which are designed to withstand waves, weather, and even hurricanes. These platforms can be modular, like floating puzzle pieces, making them adaptable, scalable, and easier to transport into position from dry land construction sites.

Here’s how key systems within a floating city typically function:

• Energy: Floating cities harness renewable energy sources such as solar, wind, and ocean thermal energy conversion (OTEC). These decentralised systems reduce reliance on mainland grids and help keep the city operational in remote settings.
• Water: Desalination systems convert seawater into fresh drinking water, while wastewater is treated on-site to support sanitation and even agriculture.
• Food: Cities often integrate aquaculture facilities and vertical farms, growing fish, seaweed, and vegetables directly on the platform or in underwater zones.
• Waste and recycling: Advanced waste management systems process rubbish sustainably, with some concepts incorporating circular economy models where waste is reused for fuel, compost, or building materials.
• Transport and access: Instead of cars, floating cities favour bike paths, water taxis, drones, or walkable layouts, making mobility low-impact and highly localised.

Importantly, these cities are designed to rise and fall with the sea, offering long-term resilience against flooding, storm surges, and shifting coastlines. In this way, floating cities don’t resist the ocean, they work with it.

What are the pros of floating cities?

Floating cities offer a compelling solution to some of the most pressing challenges of the 21st century, particularly around climate resilience, urban overcrowding, and sustainable development.

Here are some of the key advantages:

• Climate change adaptation: Floating cities rise and fall with sea levels, making them naturally resistant to flooding, storm surges, and coastal erosion; ideal for low-lying nations and vulnerable coastal regions.
  
• Flexible, modular design: These developments are scalable and adaptable. Sections can be added, removed, or relocated, allowing cities to evolve with the needs of their population.
  
• Land-free expansion: With urban land becoming scarcer and more expensive, the ocean offers a new frontier for development, particularly for island nations and megacities with limited space.
  
• Self-sufficiency: Many floating city designs incorporate renewable energy, water desalination, waste recycling, and food production, reducing dependence on mainland infrastructure.
  
• Environmental cohabitation: Some floating cities are designed to regenerate marine ecosystems, using materials like bio rock to create artificial reefs that promote aquatic life and biodiversity.
  
• Disaster resilience: Well-engineered floating cities are built to withstand harsh weather and, in some cases, even category 5 hurricanes, making them an attractive option for disaster-prone regions.

In short, floating cities could offer not just an alternative, but an improvement over conventional urban planning in certain parts of the world.

What are the cons of floating cities?

Despite their futuristic appeal, floating cities face significant technical, environmental, and social challenges that must be addressed before they can scale.

Some of the main concerns include:

• High initial cost: Building on water requires specialised materials, engineering, and logistics, making upfront investment much higher than typical land-based construction.
• Regulatory complexity: Maritime law, zoning, and jurisdictional ambiguity present unique legal challenges. Who owns the water? Who governs the population? These are questions that still lack clear answers.
• Maintenance and durability: Saltwater is highly corrosive. Maintaining structures exposed to marine conditions over decades will require robust materials, frequent inspections, and innovative construction techniques.
• Infrastructure and connectivity: Floating cities must develop or import their own systems for energy, water, waste, transport, and digital infrastructure. Connecting to mainland services isn't always viable.
• Ecological disruption: Poorly planned projects could harm marine ecosystems through shading, waste leakage, or changes in current flow, highlighting the need for marine-sensitive design.
• Social and cultural challenges: The idea of living permanently on water may not appeal to everyone. Community cohesion, mental health, and access to traditional land-based activities may also be harder to maintain.

Like any new frontier, floating cities come with trade-offs, but with the right investment, governance, and public engagement, many of these challenges can be mitigated.

What is an example of a floating city?

Floating cities may sound futuristic, but several real-world projects are already underway, ranging from experimental neighbourhoods to full-scale marine metropolises. These developments showcase different models of floating infrastructure, from small-scale residential hubs to high-tech, self-sustaining urban ecosystems.

Here are some of the most notable examples:

Oceanix City

Oceanix City is one of the most advanced floating city concepts currently in development. Supported by the United Nations Human Settlements Programme (UN-Habitat), the project is being designed to accommodate up to 12,000 people in a network of hexagonal, floating platforms.

Each module, measuring about 100 metres across, will house approximately 300 residents and include essential services such as healthcare, education, retail, food production, and renewable energy infrastructure. The design is fully modular, meaning that additional platforms can be added over time to grow the city.

Oceanix’s goal is to build a climate-resilient, zero-waste, self-sustaining floating urban system. The first operational village is expected to launch as early as 2025, starting with six interconnected platforms.

Dogen City

Dogen City, designed by renowned Japanese architect Toyo Ito, is a far more ambitious concept, slated for possible development by 2045. This circular floating megastructure would measure 4 kilometres in diameter, housing up to 40,000 people.

The city’s interior would feature adaptable floating pods that can be reconfigured as needed, surrounded by a massive ring structure that acts as a tsunami shield. Facilities would include residential zones, research centres, food production systems, and even launch pads for spacecraft.

Dogen City would also integrate underwater data centres, using the ocean’s natural cooling to reduce energy costs, an innovative solution to the growing environmental burden of digital infrastructure.

Oxagon

Oxagon is part of Saudi Arabia’s NEOM project, envisioned as a floating industrial hub powered entirely by clean energy. Planned for completion by 2030, Oxagon will span approximately 7 kilometres and is expected to host 100,000 residents.

Rather than focusing on housing, Oxagon will serve as a centre for advanced manufacturing, innovation, and global trade. It’s being designed with cutting-edge logistics, AI integration, and sustainable infrastructure in mind.

This project showcases a more commercial application of floating infrastructure, demonstrating that marine cities could also play a role in global industry, not just residential life.

Floating village in Amsterdam

Perhaps the most grounded example to date is the floating village developed in Amsterdam. This small-scale, fully operational community includes 46 homes housing around 100 residents, all floating on the water.

The project is proof that floating urban living isn’t just theoretical, it’s already happening. With built-in climate resilience and a focus on energy efficiency, the Amsterdam model serves as a prototype for scalable urban developments across Europe and beyond.

What is seasteading?

Rather than building ever-higher sea walls to hold back rising ocean levels, a growing number of architects, engineers, and futurists are exploring the opposite approach: constructing homes, infrastructure, and entire communities that float on the sea itself. This concept is known as seasteading.

At first glance, it might sound like a sci-fi fantasy, but in practice, it’s not as far-fetched as it seems. In fact, we already have working examples of “floating communities” all around us.

Oil rigs, for instance, routinely house hundreds of workers in fully functional living and working quarters far out at sea. These structures operate independently for long stretches, proving that ocean-based human habitation is not only possible, but it’s a normal part of industry. The same goes for cruise ships and cargo vessels, which carry thousands of people across oceans daily, effectively functioning as mobile floating towns.

Seasteading builds on these examples but reimagines them for broader civilian use, offering a vision of resilient, water-based cities that could offer safety, sustainability, and autonomy in a world facing climate-driven displacement. As coastal populations face mounting risks, the idea of turning water from a threat into a platform for living is gaining serious traction.

Are artificial islands the answer?

If floating a city on a giant shipyard isn’t feasible, what about building new land altogether?

Artificial islands, also known as land reclamation, have been used for centuries. This method involves depositing massive amounts of rock, sand, and clay into the sea to create new terrain above water. Countries like the Netherlands have successfully reclaimed land for agriculture and development, and modern examples include projects like Dubai’s Palm Islands.

But while land reclamation works, it’s not without major drawbacks. It’s expensive, environmentally disruptive, and often unsustainable, especially in an era of climate uncertainty. Altering the seabed at scale can damage marine ecosystems and create erosion or flooding risks in neighbouring areas. It’s also a static solution to a dynamic problem: reclaimed land still sits at sea level, making it vulnerable to the very rising tides it’s meant to withstand.

So while land reclamation has its place in the history of coastal expansion, it’s not the most future-proof strategy for dealing with long-term sea level rise.

What’s the real solution to building floating cities?

The most promising approach isn’t one enormous floating structure or artificial land, it’s a modular network of smaller, interlinked platforms that float together in harmony with ocean movement.

These floating systems are already in development. In Amsterdam, for instance, architecture firm Waterstudio has collaboratively created a floating neighbourhood of 46 homes, housing 100 people. The development is not just flood-resistant, it’s self-sufficient. Like a cruise ship that never docks, it generates its own energy, manages its own water supply, and operates largely independently from the mainland.

One especially innovative system behind these cities is Ocean Thermal Energy Conversion (OTEC). This renewable energy technology leverages the temperature difference between warm surface water (around 25°C) and colder deep water (around 5°C) to generate electricity.

Here’s how it works:

• A low-boiling-point liquid like ammonia is vaporised using the warm water.
• The expanding vapour spins a turbine, which powers a generator.
• Cold water from the ocean depths is then used to condense the vapour back into liquid, restarting the cycle.

But the benefits don’t end there. The cold waste water can also be used in aquaculture systems to raise fish and algae, and to desalinate seawater, creating a closed-loop that provides food, water, and energy from one integrated system.

In other words, floating cities aren’t just about staying afloat; they’re about staying self-sufficient.

What is seament (bio rock) and how does it help construction?

As floating cities develop, architects and engineers are turning to innovative materials that can thrive in marine environments, and one of the most promising is bio rock, also known as seament or seacrete.

At first glance, it sounds like something out of science fiction, but bio rock is a real, proven technology. The process is based on a simple electrochemical reaction:

• A steel bar is submerged in seawater and connected to a low-voltage electrical current.
• The bar acts as a cathode, attracting minerals from the seawater (mainly calcium carbonate).
• Over time, these minerals crystallise into a hard, limestone-like coating, creating a material that’s comparable to concrete in strength but forms naturally in the ocean.

This limestone coating continues to thicken over time, reinforcing the structure without heavy industrial processing or emissions. The result? A self-healing, eco-friendly building material that bonds with the ocean floor and becomes stronger the longer it’s in use.

But the benefits of seament go beyond durability:

• It forms artificial reefs, providing shelter and breeding grounds for marine life.
• It helps anchor floating structures to the seabed in a way that’s more organic and less invasive than traditional foundations.
• It’s resilient to corrosion and can withstand powerful storm conditions, including category 5 hurricanes.
  

In the context of floating cities, seament represents a sustainable construction method that not only protects against the ocean, it works with it, fostering marine ecosystems while enabling long-term, climate-resilient infrastructure.

As we look toward future ocean-based development, bio rock could become the foundation - literally - for the next generation of coastal architecture.

Could floating cities be a cheaper, more sustainable future?

While the idea of floating cities might evoke images of high-tech luxury and billion-dollar infrastructure, the reality is that they could eventually become more cost-effective and sustainable than traditional land-based development.

Here’s why:

• No need for expensive land acquisition: Coastal land is becoming increasingly scarce and prohibitively expensive in many parts of the world. Floating cities bypass this entirely by building on international or municipal waters, significantly reducing real estate costs.
  
  
• Lower long-term operational costs: Although the initial construction costs are high, floating cities are designed to be self-sufficient, generating their own energy, food, and fresh water. Over time, this reduces dependency on external utilities and can lead to lower operational expenses.
  
  
• Built-in climate resilience: Floods, storm surges, and sea level rise are costly to defend against in conventional cities. Floating cities are naturally adaptive, rising and falling with water levels, potentially saving billions in disaster mitigation and infrastructure repair.
  
  
• Shared, modular infrastructure: With modular platforms, construction is scalable and more efficient. Resources like transport, waste processing, and power systems can be centralised and shared, reducing waste and duplication.
  
  
• Opportunities for affordable housing: As technology and material costs decrease, floating homes could become a viable alternative to land-based housing, especially in areas prone to displacement from climate events. In some cases, projected prices for floating properties are around £200,000, competitive with or even cheaper than urban housing markets.

Floating cities offer not just a novel way to live, but a reimagining of urban life that's built around sustainability, resilience, and efficiency. As the climate crisis continues to reshape how and where we live, the ocean could become an affordable frontier for future communities, especially for populations displaced by sea level rise or environmental disasters.

When will floating cities become a reality?

Not long ago, the idea of living in a floating city might have sounded like something out of a science fiction film, perhaps one starring Kevin Costner, gills, and an apocalyptic ocean. But today, the timeline for these developments is no longer speculative; it’s measurable.

Several projects are already in motion:

• Oceanix City, backed by the UN, is expected to launch its first community by 2025.
• Oxagon, Saudi Arabia’s floating industrial hub, is scheduled for completion by 2030.
• Dogen City, the most ambitious of the lot, has a projected opening date of 2045.

And beyond the headline-grabbing megaprojects, there are floating communities that already exist, such as the Waterstudio-designed floating village in Amsterdam, home to over 100 people.

What’s remarkable isn’t just the ambition, it’s the urgency and funding behind these plans. Governments, developers, and climate-conscious urbanists are recognising that floating infrastructure could be key to solving real-world problems: rising seas, housing shortages, energy insecurity, and disaster displacement.

Of course, there are hurdles. High construction costs, regulatory ambiguity, and public scepticism still stand in the way of widespread adoption. But with climate change accelerating and coastal populations under growing pressure, the incentive to innovate is strong, and growing stronger.

As designs improve and technologies mature, floating cities are likely to shift from experimental prototypes to viable alternatives for housing, commerce, and community, sooner than many expect.

Get in touch

Floating cities are no longer just a concept; they’re a signpost for how we might adapt to the challenges of tomorrow. With climate resilience, sustainability, and smart design at their core, these projects could redefine not just where we live but how we build.

At Lyon, we’re always tracking the latest innovations in construction, sustainability, and urban design. Whether you're a developer exploring future-ready infrastructure or a business interested in smart building solutions, our team can help you stay ahead of the curve.

Get in touch today to learn how emerging technologies like floating architecture could impact your industry, and how you can prepare for what’s next.