Nothing dates faster than the future. That is why architecture, the slowest of the arts, is probably the worst medium to express it. But that hasn't stopped architects trying and their futuristic fantasies have been hugely influential in our cities. This was never more so than in the early 20th century, when the modernists conceived of rational cities that would replace random street-patterns with gardens spiked with skyscrapers linked by streets in the sky. The best ended up like London's Barbican (yes, the best), the worst like the decaying housing projects that circle nearly every major city.

So it is entirely appropriate that Future City, a paean to architectural utopias, should sit in the Barbican, London's last chunk of architectural utopianism. (Conceived in the 1950s, it was finished only in the 1980s, when it was already painfully passé.) Future City is an attempt to display architecture's most radical visions from the lasthalf-century. It is a superb collection of stuff, with fantastic, visionary drawings, pasted-together manifestoes and stunning models.