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A New Interface between Humankind and the Deep Sea
-A Deep Sea Future City Concept-

An Idea to Connect Vertically with the Deep Sea

Approximately 70% of the earth’s surface is covered by the ocean, and the ocean itself consists of approximately 80% deep sea.
The deep sea offers enormous potential for ensuring effective and appropriate cycles and processes in the earth’s biosphere.
Unfortunately, we have yet to make the most of this potential.
This large-scale concept seeks to take advantage of the limitless possibilities of the deep sea by linking together vertically the air, sea surface, deep sea, and sea floor.
Now is the time for us to create a new interface with the deep sea, the earth’s final frontier.

Breaking free from past patterns of land development, which have focused mainly on efficiency, this plan is intended to promote true sustainability while maximizing use of the deep sea’s resources.

Brochure PDF Download

The OCEAN SPIRAL Concept for a Deep Sea City of the Future
Harnessing the power of the deep sea in order to renew the earth

MASTER VISIONVertical unification of the sea surface with the deep sea


The Ocean Spiral base camp

Blue Garden is a sphere measuring 500m in diameter that floats in the deep sea like a spaceship.
This city is even safer and more comfortable than the land-based ones we all know.

  • A comfortable city with minimal temperature changes
  • A safe city unaffected by typhoons or earthquakes
  • A healthy city with higher concentrations of oxygen than on the ground

The Blue Garden’s grand entrance

The Blue Garden’s atrium

A New Lifestyle
In the Casual Zone facing the deep sea, people can experience and enjoy the deep sea, while learning about and discussing its unique qualities.

Deep sea sightseeing tours
Hands-on education on the deep sea
Deep sea high-concentration oxygen therapy
Comfortable and safe places to live and work

The Blue Garden’s deep sea promenade

New Business Models
The Business Zone of the central tower
incubates business models for new deep sea industries.

Deep sea resource industries
Deep sea energy industries
Deep sea tourism industries
Advanced deep sea research facilities

The Blue Garden’s central plaza


Integrating the functions required
because of the deep sea

  • Electricity: Power generation based on ocean thermal energy conversion
  • Food: Aquaculture using deep sea water
  • Fresh water: Desalination using water pressure
  • Transportation: Port (supply base) for deep sea submersible probes
  • Information: Deep sea monitoring facility




Developing tomorrow’s advanced deep sea
industries based on today’s up-to-date
deep sea research

  • CO2: Storage and reuse of industrial carbon dioxide emissions
  • Resources: Development and cultivation of deep sea resources



SOLUTIONEarth regeneration by potentials of the deep sea

Renewing Global Cycles in Five Areas
Harnessing the potential of the deep sea to renew the earth’s cycles
and processes and to create a more sustainable human society in five critical areas

TECHNOLOGYTechnological challenges for the future

Structural Design: Building a Submerged City of Concrete, 500m in Diameter

Using a spherical shape to withstand water pressure

High-strength resin concrete

Reinforcement bars
Rustproof resin bars

Environmental considerations
Use of materials recycled from PET beverage containers in the resin concrete

Spherical concrete lattice shell of 500m in diameter

Using an internal tower to reinforce the sphere’s shell

Exterior Wall Design: Tackling the Challenge of Building a Transparent Sphere with 360° Panoramic Views of the Deep Sea

Realized using triangular acrylic plates measuring 50m each a side

Reinforced using semitransparent FRP ribs

Using microbubbles and other means to prevent the adhesion of marine life

Sealing against water, absorbing displacement etc,

Building a spherical shell with triangular acrylic plates measuring 50m on each side

360° panoramic views of the deep sea

Indoor Environment Design: Challenge to Achieve the Comfortable Environment Making  the Best Use of the Conditions of the Deep Sea.

Natural convection
Using temperature differential between the sea water and air to ensure the natural convection with comfortable and cool air

Using the cooling source of deep sea water to ensure comfortable dehumidified air conditioning

Air conditioning
Reusing chilled water after dehumidification to ensure comfortable radiant air conditioning

Thermal insulation
A comfortable environment due to the insulation effects of acrylic plates (3m thick)

Construction Plans: Challenge to Achieve Fully Automated Maritime Construction of the Sphere

Early adoption of future technologies
3D printing construction method (Pouring resin concrete, resin bars)

Integrating proven technologies
Automated vertical diversion of large-scale concrete forms Jump-up method
Balanced cantilever Dywidag method

Construction methods specific to maritime construction
All construction work undertaken at the sea surface (Submersion of completed structure)

Construction steps

Operation and Maintenance Plans: Fail-safe Features and Maintenance

1. Control of vertical movement: Super ballast balls filled with sand

Wave control:
Floating seawall
Control of everyday vibrations:
Vibration-damping equipment

VARIATIONCompatible with various sites and scales

Site Variations: The OCEAN SPIRAL Network, Connecting the World’s Seas

Candidate sites based on regional characteristics

1. Coastal seas: Stimulating economy on remote islands in exclusive economic zones
2. Seas of island nations: Countering rising sea levels in Pacific island nations
3. Seas in desert regions: Comfortable deep sea living in the seas of the Middle East and Africa

Candidate sites based on sea floor topography

Source: The Deep Sea and its Denizens−A World of Beautiful Mysteries (Full-color illustrated) (Natsumesha CO.,LTD.), Japan Agency for Marine-Earth Science and Technology (JAMSTEC),supervision.; illustrations by

Scale Variations:

In addition to the city-scaled 500-m diameter model, a more practical architectural-scale 200-m diameter model is prepared.

500-m diameter (city model)

200-m diameter (architectural model)


The following parties provided technological information for the OCEAN SPIRAL concept for a deep sea city of the future:

  • Academic advisors
    Marine ecosystems, deep sea water
       Masayuki Takahashi, Professor Emeritus, University of Tokyo, Kochi University
    Ocean thermal energy conversion
       Professor Yasuyuki Ikegami, Saga University
  • The deep sea
    Japan Agency for Marine-Earth Science and Technology (JAMSTEC)
  • Specialized fields
    Fisheries resources, aquaculture
       Fisheries Research Agency
    Resin concrete, resin building materials
      Showa Denko K.K
    Large-scale acrylic plates

Comments from the Japan Agency for Marine-Earth Science and Technology (JAMSTEC)

The Japanese Islands is located in one of the earth’s most geologically active regions. JAMSTEC has long sensed its responsibility to transmit from Japan to the world an integrated understanding of the sea, the earth, life, and human activity. Current social trends and issues point to the urgent need to promote maritime innovations in areas ranging from the use of marine resources to the deployment of marine biotechnology, not to mention the need to advance our understanding of the sea and earth. When we heard of Shimizu Corporation’s concept for a deep sea city of the future, one designed to serve as a new interface between humanity and the deep sea, we felt confident Shimizu would find our research findings useful. JAMSTEC’s mission is to help establish Japan as a leading maritime power through new science and technology and to contribute to and maintain sustained progress for the Japanese public, human society, and the earth. Beyond providing information based on JAMSTEC’s achievements for use in preparing this brochure, we are fully committed to joint efforts to improve the technological efficacy and feasibility of the OCEAN SPIRAL project.

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