Maybe something like The Ocean Spiral -- an underwater metropolis that generates energy from the seabed and is capable of providing homes and accommodation for 5,000 people.

Sure, such blue-sky thinking may only seem plausible in the world of Hollywood CGI, but this is the futuristic concept proposed by Japanese construction firm Shimizu Corp.

According to literature released by the company, expertise is being sought from Tokyo University, Japanese government ministries as well as energy firms to bring the project to life.

Shimizu also say projects like the Ocean Spiral may be necessary in the future to confront increasing global problems such as rising sea levels and the need to create new, clean energy sources.

Under the sea

Divided into three distinctive zones, the structure will stretch all the way to the crushing black depths 2.8 miles under the sea off the coast of Japan.

A giant sphere with a diameter 500 meters (1,640 feet) situated just below the surface will form the first section and house residential zones, businesses and hotels.

This inhabited area will be connected to a nine-mile spiral (section 2) that that descends to the seabed where a deep-sea submarine port and factory (section 3) will create the energy required to power the sphere by using micro-organisms that turn carbon dioxide into methane.

If that's not high-tech enough, power generators situated along the spiral will then use differences in seawater temperature to create additional energy by applying thermal conversion technologies.

Technology wait

Shimizu has a history of imaginative, high-concept projects including a space hotel and floating botanical cities.

The company says the Ocean Spiral would take five years to build and the technology required will be ready in 15 years.

Funding for what is likely to be a cash intensive exercise will also have to be secured.

Until such times arrive, all we're left with is a series of cool artist renderings to whet (or should that be wet?) our appetites.

(CNN)