Six contenders, including the Glucksman Gallery in UCC, are in the running for the 2005 Stirling Prize for architecture writes Frank McDonald, Environment Editor

The choice of Edinburgh as the venue for this year's Royal Institute of British Architects (RIBA) Stirling Prize gala dinner on Saturday evening doesn't necessarily mean that the controversial Scottish Parliament has already been anointed. Quite the reverse, as the Scots would say.

It is up against stiff competition from buildings by Will Alsop, Norman Foster, Zaha Hadid, Bennetts Associates and our own O'Donnell and Tuomey, no strangers to awards. Indeed, the odds offered by bookmakers when the shortlist of six was first announced in July made the parliament a rank outsider.

Designed by the late Enric Miralles, who died long before it was built, this almost volcanic eruption below the Salisbury Crags was described by the jury as "a remarkable architectural statement which has an enormous impact", not least due to its "series of extraordinary spaces and their changing effects".

There is barely a straight line anywhere, inside or out. Everything apart from the doors and stairs is curved, twisted or warped. And parts of the complex, notably the garden foyer with its leaf-shaped rooflights running this way and that, seem to swirl in space - suspended there as if their only function is to entertain.

"The intellectual vision was for a unique institution - open, anti-classical and non-hierarchical," according to RMJM, the Edinburgh architects which collaborated with Miralles. So the architecture is "de-institutionalised, aggregated and organic . . . defying all the canonical rules of architectural composition".

Noting an inscription on the parliament's memory wall, "say little and say it well", the jury concluded: "This building is definitely saying a lot rather than little, but it definitely says it well." And even though it reeks of Barcelona amid the dour grandeur of Scotland's capital, it has already won six major awards.

The jury was clearly bowled over by Zaha Hadid's new Central Building for BMW's factory in Leipzig. "Powerful yet svelte, it is almost coquettish in its allure. The embodiment of Zaha's sinuous, sensuous architecture. It is hard to do justice in words to architecture at this level," its citation gushed.

As conceived by the Baghdad-born Diva of Deconstruction, who won the Pritzker Prize last year, the BMW Central Building is the nerve-centre of the whole factory complex, "the point of confluence and culmination of the various converging flows" such that it becomes a "force field" of scissors-like cascades.

"You know on entering that car production is the central function, thanks to the nice conceit of half-finished Beamers gliding above your head on elevated conveyor tracks, making their silent stately way between the body shop and the paint shop, weaving above 500 office and production staff".

Hadid has attributed her success to a refusal to compromise. In response to criticism that some of her swirling designs were unbuildable, she said: "I have managed to show that architecture is not only one thing and, with the help of my entire team, I've been able to discover new possibilities."

Another car factory - this one for designing, developing and building Formula 1 cars - has won a place on the shortlist for Foster and Partners, which walked away with last year's Stirling Prize for 30 St Mary Axe, the London headquarters of insurance giant Swiss Re, quickly nicknamed "The Gherkin".

The McLaren Technology Centre in Woking, Surrey, was described by the jury as a building that "symbolises McLaren", built with great precision, like their cars. "You arrive having travelled around a lake, in Foster's words, 'as if driving up to a country house'. But the experience is more akin to Arthur C Clarke than Agatha Christie."

Brainchild of Ron Dennis, who heads TAG McLaren, this super-cool 57,000sq m (613,542sq ft) building was hailed by Icon magazine as "part brand, part factory and part [ his] vision of future working environments . . . from the wind loads on the glazed cladding system to the optimum amount of hand soap dispensed in the lavatories".

One suspects, however, that the users of Will Allsop's Fawood Children's Centre in rundown Harlesden, north London, will be happier. Its enthusiastic head reported that "her charges seemed to be considerably healthier since the new building opened - a fine example of the beneficial effects of good architecture".

Although members of the jury expressed some puzzlement about the project, their overall impression was one of amusement and delight. They were particularly impressed by the concept of creating a "friendly cage" and the way it is animated by the play of light on the coloured lozenges of the main façade.

Designed to provide a safe play space for pre-school children, the shed-like enclosure contains brightly-coloured classroom units made from recycled sea containers, integrated with an outdoor environment that includes a piazza for picnics, a willow tunnel, a tree house and a water garden - all on a tight budget.

A library that's "a joy to be in", according to the jury, has also made the shortlist - even though it was levered by a public-private partnership, usually a recipe for dumbing down.

Yet the Jubilee Library in Brighton, which forms the centrepiece of an urban regeneration scheme, had been "delivered with great flair". Designed by Bennetts Associates with Lomax, Cassidy and Edwards as part of a project that also includes a hotel, apartments, offices, shops and restaurants, gathered around a new public square, the striking glass-fronted library faces the sea and also scored highly with the jury for its excellent environmental rating.

Members of the jury - Architects Journal editor Isabel Allen, veteran broadcaster Joan Bakewell, engineer Max Fordham, architect Piers Gough and RIBA president Jack Pringle - were even more impressed by O'Donnell and Tuomey's Glucksman Gallery in UCC, of which they said: "The more one looks, the better it gets."

As their citation notes, "that is the sign of complete assurance and maturity. What most artists do is to make simple things complex; great artists make complex things appear simple. This is one of the rare buildings that fits that definition of greatness" - which is why the Glucksman is on the Stirling Prize shortlist.

The €29,000 (£20,000) sterling prize, now in its 10th anniversary year, is awarded to the architects of "the building that has made the greatest contribution to British architecture in the past year". It's only because Sheila O'Donnell and John Tuomey are members of the RIBA that the Glucksman even qualified to be considered in this context.

But Jonathan Glancy of the Guardian had no doubt that their poetic gallery in the trees within earshot of the River Lee would be "the real and enduring legacy" from Cork 2005, "an art gallery at once gracious, intriguing, rigorous and well made, a thing of unexpected beauty, and surely a joy for a very long time to come".

The Stirling Prize commemorates the late James Stirling, a Falstaffian figure in the post-modern movement during the 1980s. Coincidentally, John Tuomey worked for Stirling Wilford and Associates in London for four years after graduating from UCD in 1976, while Sheila O'Donnell also briefly worked for the same practice.