This is the Heatherwick difference. Other urban designers might have a mad inspired idea, dismiss it on grounds of practicality or unprofitability, and then do something conventional. They would use off-the-peg materials and aim for a general slight lift in quality, rather than concentrating all the effort on getting a high concept to work. They might be defeated by the thought of the physical punishment their work would receive, and act accordingly. But Heatherwick sticks with the mad idea all the way, is perfectly happy to juxtapose the sublime with the prosaic, the expensive with the dirt-cheap. Indeed, he insists on it. He specified cheap paving round the edges of the good stuff, and above all no “designer” lamp-posts - the habitual calling-card of jobsworth cityscape improvers.

Thus through unrelenting toil and large doses of charm, he makes it work his way. The Blue Carpet has turned out looking remarkably like Heatherwick’s competition-winning sketches from 1996. And when you think what “public art” usually means in the municipal mind (Newcastle has more than its fair share of bad contemporary sculpture plonked around the place) that is some achievement.

There is a civic agenda here, too. Newcastle and its riparian neighbour, Gateshead, jointly want to be European City of Culture in 2008. Much kudos and tourist money can flow from this designation, as Glasgow famously proved years back. The Blue Carpet is thrown into the bid along with the Angel of the North, the clever new opening-eye Tyne bridge, the soon-to-open Baltic contemporary arts centre, the bulbous Norman Foster concert hall now under construction, the housing designed by Wayne and Gerardine Hemingway on the site of a long-forgotten garden festival, and so on.

Southern critics tend to be buttonholed by the north-eastern media on arrival in Tyneside. They want to know: is the area making headway? Is it appearing on the contemporary-culture radar screen, or do we think of it still only in terms of soccer and brown ale? In other words, does the bid stand a chance?

It ought to. Of the great British metropolises, only Manchester/Salford is harder at work restoring its cultural image, and they had the sudden shock of a devastating city-centre bomb to concentrate their minds. But if Newcastle/Gateshead really wants to do a Barcelona with its public space, the Blue Carpet should be seen not as a one-off, but a prototype. Dozens of corners of the city could benefit from such design competitions. The cumulative effect could be remarkable. The problem is that exercises such as the Blue Carpet are still seen as special. No: they should just be normal.