CITIES under the ocean, buildings made out of mould, a futuristic “spine” that runs from Tasmania to the mainland and a roof on top of Melbourne.

Those are some of the ideas dreamed up by Australian architects as part of a project to imagine what our capital cities might look like in a hundred years.

Now + When: Australian Urbanism will be the Australian Institute of Architects’ major exhibition at this year’s Venice Architecture Biennale.

The “now” section includes stunning aerial shots of Australian cities at dusk, while “then” focuses on how they could be transformed in the future.

Both the photos and designs will be projected against an enormous screen in stereoscopic 3D, letting viewers with special glasses see the images shift as they move around the room.

One of the most striking visions of the future is Multiplicity, by Melbourne’s John Wardle Architects along with writer and filmmaker Stefano Boscutti.

In Multiplicity, the idea is to build upwards, not outwards, from Melbourne’s city centre.

A giant platform above the city is suspended by pylons between buildings, offering a space to grow food and giving shade to residents from rising temperatures in coming years.

Stefan Mee, a principal at John Wardle, said working with Boscutti had led the team to consider incorporating ideas from unusual sources like films and novels.

“He was the agent provocateur of the project. The old maxim of architects is that form follows function, but he was talking about form following fiction,” Mr Mee said.

The sustainable city

While Multiplicity may look fantastical, it was inspired by real problems faced by city planners.

“There’s a lot of debate in Melbourne about where the boundaries of growth should be for the city, and how much population growth there should be,” Mr Mee said.

“We thought it would be interesting and kind of provocative to think about what would happen if somebody proposed a much higher density — kind of a hyper-density — in the CBD.”

Mr Mee said his team was influenced by contemporary discussions about creating “greening grooves” in cities. The architects wanted to see how far they could push that idea.

“In Chicago and New York in the US they’ve been talking about doing that, and even in Melbourne there’s examples of it starting to happen,” Mr Mee said.

“But we thought, what if you actually think about that on a grand scale and even think about it in terms of agricultural production?

“So we imagined there was this pastoral landscape sitting above the CBD which people could get access to, but was also a very productive space.”

Mr Mee said that while the concept might not take off — or even be feasible — it did offer a new way of thinking about how to make Melbourne sustainable.

“It’s not necessarily proposing that this is a solution for Melbourne’s density issues, but what it is raising is some principals about how we might address sustainability,” he said.

“Melbourne’s ecological footprint at the moment is something like 28 times the actual geographical area of the city.

“If we can reduce that and compact our agricultural zone and our energy production into one vertical space above the city, then perhaps we can start to reduce our impact on the environment.”

Smart software

One of the sponsors supporting the Now + When exhibition is Autodesk, the software company behind design programs like 3ds Max and AutoCAD.

Mr Mee said his firm used 3ds Max to visualise the city of Melbourne during the creative process and that programs like it were giving architects more power over their designs.

“One of the advantages of using technology now is that you can effectively program the software to take a whole lot of things into consideration. For example, things like the way the sun falls and the best orientation,” he said.

“You used to have to use a rule of thumb, before we had the benefit of the tools we now have. Now you can actually be very precise at mapping those things.”

Autodesk executive Rob Malkin said a new generation of software was giving architects and designers the ability to see how their ideas fared in real-world conditions by replicating environmental factors.

“You know the way the sun’s going to reflect against the house, where the windows should be, how best to utilise your heating and air conditioning systems, and the air flow, to design it in the most efficient means possible,” he said.

Now + When will be shown at the Australian Pavilion at the Venice Architecture Biennale in September.