Thomas Sutcliffe: Naked prejudice in the piazza

Venice was awash with architects last weekend - in town for the architecture section of the Venice Biennale. I found myself dogging the footsteps of Maxwell Hutchinson in the Calle delle Veste and, having lunch in Campo Sant' Angelo on Sunday we happened to be seated next to two female architects engaged in a reverent discussion of the Villa Savoie - Le Corbusier's modernist masterpiece. And if that seemed a mildly perverse topic given that we were surrounded by masterpieces of Baroque and Palladian architecture it also seemed to sum up the doctrinal piety of some architects - for whom a building is less a physical object in a landscape than an expression of sacred theological principles.

What this brief section of their conversation seemed to be about was the identification of sectarian common ground. They wanted to establish that they both worshipped in the same church. I shouldn't have been eavesdropping, of course - but the tables were quite close together and in any case the conversation chimed in with something that had been niggling at me intermittently since I'd walked into St Mark's Square the day before - emerging into it after spending a couple of hours in the rooms of the Ducal Palace.

What had been on my mind was the fact that I didn't much care for the Basilica of Saint Mark - or rather, since liking it isn't that much of a problem once you start to concentrate on the matter, that my first instinctive reaction to it had been to think what a gaudy piece of trash it was. This wasn't the first time I'd seen it, and it wasn't the first time I'd felt a bit ambiguous about its architectural merits. The reflex is hardly original either, having been felt by countless previous visitors to Venice - though it's sometimes suppressed in a prose that tries to square the dutiful impression (magical, unmatchable, sublime) with the actual one (what a mess!).

I think even Ruskin might have been up to a bit of this with his description of how "as if in ecstasy, the crests of the arches break into marbly foam and toss themselves far into the blue sky in flashes and wreathes of sculptured spray". No need to consult Dr Freud about those lines, I think, though they do at least have the virtue of reflecting the unbalanced excess of the façade.

The problem with St Mark's is that it is a collective collage rather than a composition. It looks like the result of a nursery school exercise in bricolage, with bits and bobs added here and there according to when they turn up. Successful raiding party on the Turks? Stick the results here. Given the Dalmatians a hard time and ripped off a few pillars? - they'd look smashing in this bare spot by the door, wouldn't they? Appropriately enough, the presiding aesthetic of San Marco appears to be that of the souvenir hunter - crowding the mantelpiece with little commemorative knick-knacks. By chance I was reading Alan Bennett's Untold Stories at the time and he makes much the same point about St Mark's interior, though he charitably adds that "once written off as a collection of superior bric-a-brac it's full of separate pleasures". Separate pleasures, though, is exactly where the problem lies - St Mark's providing something of a problem for any aesthetic that privileges coherence and unity and simplicity over anecdotal disorder. I'm exaggerating a little, obviously - they've worked hard to make sure that there's a kind of symmetry to the treasure heap. But alongside the stark façade of the Ducal palace it can't help but look like the wrong kind of ornament - or, as Mark Twain once described it, a "warty bug".

Another way of putting this might be to say that St Mark's strikes you as an alien presence in St Mark's Square - which is hardly surprising given its origins and the Byzantine tilt of its style. But I think it's also because it's a prime example of the vulnerability of all prominent or long-lasting buildings to architects of the future. In most cases, after all, it's not ordinary people who withdraw a seal of approval from a building. What puts a building into the cold is the buildings that follow it - and though a lot of Venetian architecture has done rather well under Modernism (think of the magnificent curtain wall of the Doge's palace or the stripped-down proportions of Palladio's San Giorgio Maggiore across the water) St Mark's isn't one of them. Which is why I was struck by my neighbours' conversation, I suppose - because it made me realise that my instinctual reaction to the sight of the façade wasn't instinctual. It was a reflex twitch of sectarian prejudice that I didn't even know I had. But if "less is more" is one of your creeds, St Mark's isn't just a mess - it's heretical.