Day at the Louvre I

What is happening to the Mona Lisa? All my life she's been famous, but recently things seem to have got out of hand. She has become the world's greatest inanimate celebrity. No-one's visit to Paris is complete without a glimpse of her - so that 'at least you can say you've seen her', to borrow a phrase from Dame Edna Everidge (although, as she doesn't like being overshadowed, it's doubtful the dame would visit the Italian star these days).

The Louvre, responding to the Mona Lisa's growing popularity, have moved the picture into a much bigger room. They've erected a false wall for her, and a bullet-proof glass panel, behind which she hangs completely alone. They've decked the museum with black and white photocopies of her, complete with felt-tipped arrows pointing visitors directly to her grand new home. Each day, wave upon wave of tourists rush past all the museum's other treasures, glancing at nothing except these helpful signposts guiding them to their prey. 'There she is,' they gasp, when they first clap eyes on her. It's as if they've glimpsed an actress on the red carpet at a Leicester Square premiere. They join the five-deep crowd in front of the barrier, jostling for a better position, waving their cameras above their heads. 'I think I got a good one of her,' someone at the back of the crowd exclaimed excitedly when I was there. 'Holy shit,' squealed another, 'I think I did as well.'

And, of course, when you do clap eyes on her, there is a kind of wow moment as you take the picture in. But is it just the wow moment you get when you see anything or anyone really well-known in the flesh? It is so hard to gauge greatness when fame gets in the way. How do you separate the shock of seeing the real thing from the shock of seeing something really good? Who makes the decisions that transform some sights into so-called 'icons'? How does tourism work? Is it the tourists themselves who collectively make something a 'must-see'? What is the process? Why do so many lovely things miss out?

I should point out that I'm not suggesting da Vinci's painting is not a very great masterpiece. All I wonder is whether she merits singling out for the utterly awed attention she receives. Is the experience of looking at her - especially as you have to stand at a distance that prevents the examination of any of the picture's detail or its extraordinary paintwork (the aspect that is supposed to be possibly its main claim to greatness) - really more amazing than the experience of looking at van Eyck's great Self Portrait in the National Gallery in London? Van Eyck's picture is rarely beset by viewers, you can get really close to it and it has no protective glass to separate you from its marvels. It is also one of the paintings that I most want to own.

And do the people who flock to see the Mona Lisa actually know anything about the painting they're so keen to see? Do they know who the artist was ? Do they know when and where he painted the thing? Do they know anything about the painstaking slowness of how da Vinci worked? Do they care that they are standing so far away from the thing that they have no chance of telling whether this is the real thing or just a fake - or seeing, if it is in fact the genuine article, what makes it remarkable?

Catching the eye of the guy who thought he'd 'got a good one of her', I asked if he knew when the picture was done. 'It's really old,' he told me, 'Maybe a hundred and fifty years or more.' 'What do you think makes it such a great picture?', I asked his companion. 'It's just so awesome,' she answered, 'just so old and amazing and all that stuff.'