Future City: Experiment and Utopia in Architecture 1956-2006 At the Barbican Art Gallery, London EC2, until 17 September
Beneath the pavement, thought student revolutionaries in Paris during 1968, lay a beach.
What they did not anticipate was that after the radicalism of the urban projects that helped to inspire them has come the whole panoply of institutionalisation: collecting, curating, exhibitions and erudite catalogues.
That at least is one interpretation of Future City, a large and challenging exhibition of radical urban projects from the last 50 years at the Barbican Art Gallery.
Its exhibits are drawn from the FRAC collection in Orleans, which started amassing material in the early 1990s under its previous director Frédéric Migayrou.
The show opens with Constant Nieuwenhuys' New Babylon and the Situationists;moves through old favourites like Archigram, Archizoom and the Metabolists; takes in Rem Koolhaas and several lesser-known gems; and culminates in a series of projects that could have come from the last Venice Biennale. Making sense of such a mouthful is not easy, though the gallery's uncompromising kunsthalle-like space, as modied by Foreign Of ce Architects' (FOA's) design, is quite appropriate.
As the Barbican's head of art galleries Kate Bush writes, the Barbican is about as close as British architecture has come to a realised, radical urban vision, while FOA shows every sign of achieving more in various global locations.
But the process of institutionalisation inevitably takes its toll. Categories have to be adopted and labels applied to individuals and movements who sought to challenge all such conventions. Some are familiar, such as Megastructure and the more recent Deconstruction; others are self-explanatory, like New Urban Habitat and Inatable City. But a few are less convincing, such as Oblique City, with a single example of Paul Virilio and Claud Parent's Architecture Principe, or the catch-all Contemporary Process. Imposing a taxonomy starts to direct interpretation and perhaps even to imply an overall narrative.
Migayrou's catalogue essay suggests that it may lie in 'non-standard orders' or NSA codes. 'Digital tools and their capacity for algorithmic calculation, ' he writes, 'allow one to enter on a solid footing into the domain of a continuous formal schematism revolutionising the logic of architectural design'. That itself suggests a reassertion of architectural convention - admittedly through mathematics rather than tradition - but as a sentiment it is very much at odds with the earlier schemes on show.
The appeal of projects such as Hans Hollein's floating, cloud-like superstructure looming over Vienna is that they escape architecture and become a political statement.
In 1960 there were many clouds looming over the Austrian capital. But once form becomes classiable and encodable, it loses much of its potential for radical provocation precisely because it can be relegated to that obscure little corner of cultural production called 'architecture'.
Without a degree of interpretative grounding, radical visions will remain rhetorical gestures. A few of the projects here deserve no more than that, but overall they represent a huge collective intellectual and imaginative endeavour to endow urban life with new opportunities.
How to create an interpretive framework for the recent past is a vexing question for cultural commentators. This exhibition, and the collection from which it is drawn, allows that effort to be seen as more than just a series of fragments.
Though there is still some way to go before its real implications can be understood, the exhibition and its catalogue are a worthy starting point.
Jeremy Melvin is an architectural writer and teacher in London