TECH boffins have unveiled plans for a bizarre floating city likened to a real life Noah's Ark.

The ocean-based metropolis would provide a "self-sufficient habitat" for 40,000 people, designers in Japan say.

The developers, N-Ark, even claim the zone - named Dogen City - would be resilient to an apocalypse.

Measuring 4km in circumference, the plan would be for inhabitants to be able to get to any point in the zone within an hour.

A range of buildings, including a sports stadium, is proposed, and properties would be able to be moved by sailing them to another location.

The infrastructure is circular in design to protect it from severe weather and consists of three infrastructure types.

These are a habitable ring containing the main habitable zones, an undersea data centre and medical research facilities, and flexible inner ring structures that can move freely in the inner bay.

N-Ark's development roadmap currently earmarks the year 2030 for completion, and designers see the city as a sea-based version of Elon Musk's SpaceX.

They explain: "New Ocean is a term intended for the ocean version of the private space business innovation 'New Space' started by Space X.