The Venice Biennale, which this year is devoted to cities, is a sort of Spring Show for architects, writes Frank McDonald, Environment Editor

Most of us now live in cities.This year, for the first time in human history, more than 50 per cent of the world's population (currently 6.5 billion) live in urban or suburban areas, compared to only 10 per cent just over a century ago. So the focus on cities in this year's Venice Biennale couldn't be more timely.

Ricky Burdett, professor of architecture at the London School of Economics and adviser to Mayor Ken Livingstone, travelled all five continents to put together an exhibition under the title "Cities, Architecture and Society" with the avowed purpose of stimulating public debate about urban futures.

Venews, Venice's "What's On" guide, suggested that his agenda is to seek "a new role for architecture in the great urban complexes of the future, which risk becoming even more bulimic and incontinent than what went before". As such, the 10th Architectural Biennale is "far removed from tomfoolery and the doodling of intellectualoids (sic)".

It is a serious effort to transcend the "building-as-object" approach to architecture by locating it in the wider context of the city and society, including the economy, globalisation, democracy, social justice and sustainable development.

For without good governance, as Burdett said at last week's opening, "there are no good cities".

His globe-trotting produced results - a stunning presentation of 16 major cities in the Corderie, a former rope-making plant of the Arsenale di Venezia.

This 300-metre-long building - more than twice the length of Stack A (or CHQ) in the Custom House Docks - is an enfilade of "city rooms", each one telling its own unique story.

The high point of the exhibition is a series of three-dimensional polystyrene barographs - for all the world like ice sculptures - representing the vastly different urban densities of Barcelona, Berlin, Bogota, Cairo, Istanbul, Johannesburg, London, Los Angeles, Mexico City, Mumbai, New York, Sao Paulo, Shanghai and Tokyo.

Milan and Turin are also included, as a gesture to the host country, and even Genoa gets a look-in (it's the home town of Renzo Piano). But the main focus is on the mega-cities, with maps, satellite images, plans, hopes and dreams. Some of the stated "facts" are wrong though; New York's population is eight million, not 18 million.

Each of the featured cities has its own slogan. Tokyo calls itself a "City of Flux", Mumbai a "Port of Opportunity" and Barcelona "A Model Compact City". London sees its future in "Filling the Gaps", while Cairo is characterised by "Chaos and Harmony" and Berlin, with its falling population, describes itself as "Reunited but Static".

The city frankly admits it has "run out of money", suffers from high unemployment and has problems accommodating immigrants. But Berlin says it still "offers its residents - especially young people, artists and families - a high quality of life due to its relatively low growth, low cost of living and spacious but affordable housing".

China pops up almost everywhere. It has its own temporary pavilion in the Arsenale, and both Denmark and Hungary have given over their national pavilions in the Giardini to Chinese-themed exhibitions, while the entire façade of the Italian pavilion, columns and all, is plastered with a picture of a spaghetti junction in Shanghai.

The French have turned their neo-classical villa into a commune, inspired by Paris-based architect Patrick Bouchain, who has made similar transformations in Nantes, Calais and Marseille. There's an open kitchen, a bar, reading and sleeping areas, and a scaffolded structure that leads up to a sauna and paddling pool on the roof.

Bouchain claims that the "occupation" of the French pavilion is "an architectural act" that recalls the "revolutionary excess" of exultant crowds overrunning royal palaces and aims to give people "an opportunity to experience architecture at first hand". It has certainly proved very popular, judging by the queues last week.

The French brochure includes a caustic commentary on the frenzy of development in Dubai, describing it as "pure, unabashed, outrageous consumption" with no regard for the need to conserve resources. The Gulf sheikdom's grandiose property projects, it says, "are probably the very last great folly humanity will be able to afford".

Twenty younger Italian architects (i.e. aged between 30 and 40) have put forward a utopian plan for a new city called Vema, which they suggest should be located between Mantua and Verona. Through it, they explore such issues as housing, workplaces, the human body, art, infrastructure, media, green areas, leisure and energy use.

According to Richard Rogers, who won the Biennale's Golden Lion award for lifetime achievement, "creating more compact cities through better design which responds to social and environmental concerns is the only way we will create a more desirable form of urban living and reverse the drift of people from cities to the countryside".

Ireland's entry, From Sub-Urban to Super-Rural, which pulls no punches about what's happening at home, was described by Ricky Burdett as "one of the key exhibits" of the entire Biennale. Speaking at its official opening last Friday, he applauded its polemical tone and the ability of Irish people to "turn yourselves upside down".

Paul Kelly, of FKL Architects, who had the task of co-ordinating eight other practices in presenting Ireland's entry, rejected any notion that ideas such as "sinkable" holiday homes or a rail bridge linking Rosslare with Fishguard were flights of fancy. They were "provocative proposals that would stimulate debate about the way we're going".

Gary Lysaght, partner in FKL, said Ireland needed to find a way forward between the entrenched positions of "build nothing anywhere" or "build whatever you like wherever you like". The only way of building sustainably, he suggested, was to make every house is self-sufficient, with zero carbon dioxide emissions.

"Ninety per cent of us live in houses, and many of these houses now have more toilets than people in them. You can't just say that everyone should be living in apartments, because they won't do it. People from China or central and eastern Europe are more suited to apartment living because they make good neighbours."

The basic problem, as FKL's Michelle Fagan sees it, is that Irish people "don't like communal living - the bigger the distance between you and your neighbour, the better. But we're much more spatially aware now and people building houses are interested in design - they've changed from flock wallpaper and corduroy couches to Habitat."

Fifty countries are participating in the 10th Architectural Biennale, which is "a sort of Spring Show for architects", as one visitor put it.

The Royal Institute of the Architects of Ireland will be holding its annual conference in Venice in November before the exhibition closes on November 19th. Check out reactions on www.venicesuperblog.net