Everywhere verticals, lines up and down, up and down, breaking the picture into ten thousand frames, nude descending a staircase, Muybridge's horse raising all four feet, peer through the slits and see slices of the city, terrace terrace terrace, tower block, spire, five floors up look down on the dustbins, fifty feet up look down on taxis, all around pointers up not to heaven but to the airspace, latticed with links of possibility - flight paths, jet streams, satellite links, radio waves, data channels, criss cross criss cross the sphere, closer and closer the web of communication tightens, around the buildings reaching upwards. So the gap between closes, the buildings push up, and the net meshes in, and there is no more sky.

But if you stand on Blackfriars railway bridge, rooted in a medieval name and solid Victorian enterprise, you can take a sweep of the city, a panorama like a dutch engraver, record it in sharp black lines, right around, a horizontal to counteract the verticals and the diagonals above. You can trace it continuously, erratic but unbroken, up and over, along a portico up over a dome, round a wedding-cake spire, over a melon of green glass, along a chocolate box of gold steel, a spiky marzipan concoction of gothic towers. Idiosyncratic, eclectic, anachronistic, multicoloured, undisciplined and energetic, it thumbs its metropolitan nose at the getters and spenders thrusting up into the airy net.

You gotta do the work though; you gotta stand still in the right place and look for it. You gotta track it round and see it as a whole and as a procession of pieces. It's not just a cityscape, and it's not just a blur of buildings. It's a random lovely meaningful haphazard living thing like a DNA diagram, but you have to take the effort to see it.

Wrapped up in there, hidden by the dirty streets and the filthy materialism, trampled under the feet of a million tourists and swamped by the lunch wrappers of a million school parties, are the treasures of civilisation - offered freely to all who pass by. The accumulation of centuries of learning, centuries of aestheticism, centuries of intrepid pursuit of knowledge, heaped up in mounds all anyhow. Come and drink deep, there is enough for all.

Of course, it you have money there is even more to enjoy. You can, for example, linger as long with the money changers as you spend in the temple, for the money changers have put a great deal of cunning into displaying their wares. Why sometimes they look lovelier than the objects in the temple. The buyer sand sellers claim a perfect right, because after all, do not their efforts keep the roof of the temple from falling quite in? Their efforts, and those princes of mammon who achieve immortality by bequeathing a wing or two. All freedoms have their price - and it seems that the price of access of beauty and learning is homage to mammon. OK.