The dark bulk of Bankside Power Station rears up into a clouded sky. In front, fork-lift trucks roll through the rubble. And in front of them stands Lars Nittve - an unassuming Swede in a grey double- breasted suit and striped shirt that make him look more like a banker or a lawyer than an artistic visionary - posing for a photograph.
Soon we are standing in the vast turbine hall of the power station. "Here, you will come in," says Nittve enthusiastically, "and after your 'Wow!' you can find out what is going on in the gallery, and here you will also have your first art experience, hopefully something grand and amazing." This is a great hollow space, 500 feet long and 100 feet high. At the moment, the smell of solvent hangs in the air; dusty shafts of light stream through high windows at either end, and the space hums with the roar and crash of building work. When it's finished it will still be a breathtakingly large hall, and even the most impressive sculptures of the Tate collection will look pretty dwarfed.
Nittve does his best to dispel my feeling that this ocean of space will overwhelm the art inside it. "I, too, was a bit personally worried," he says. "But I have been in discussion with artists about commissioning new work for this area, and they all say 'Fantastic'. We will not necessarily use only huge Richard Serra-type sculpture here, but also projections, or screens, and all sorts of other things. Many different artists have looked at this space. They are very diverse, but they are all very happy to address this space. It is a once-in-a-lifetime thing." As director of this brand new gallery, opening exactly one year from now, it is Nittve's job to sound upbeat and optimistic. This will be, it is devoutly hoped, the museum that will lay to rest for once and for all any suggestion that the British can't take their art seriously. For the past few decades, the British have looked to the Museum of Modern Art in New York or the Centre Pompidou in Paris and have seen only a symbol of our own inability to keep up. It's interesting that we had to get a Swede in to do the job for us, but we shouldn't hold that against Nittve. He's an enthusiastic, clever man, and although he sometimes sounds more like a walking press release than the art critic he once was - well, how would you talk if you were overseeing a pounds 130m project in a foreign country? We cross through the turbine room and into the boiler rooms, which will become the gallery spaces. The galleries will take up three of the seven levels here, and most of them will have some natural light pouring in through the sides or from above, thanks to a new glass roof on top of the power station. We struggle through rooms littered with plasterboard and at one point enter a gallery that looks almost finished, a double height room with one high, narrow window running floor to ceiling. This room is already light and white, like the best galleries. To add to the effect, in the middle of the floor sits a set of steel boxes, while in one corner squats a giant piece of cobalt blue machinery. You wouldn't be surprised if they had tags on them saying Richard Wentworth: Divorce, or Carl Andre: Equivalent IX. "It looks like you've already started moving the exhibits in," I say to Nittve, and he giggles politely. What does he think will inhabit this room when the hanging starts? "The great thing about this room is its height. I would like to use the whole height. I think I would like to show a Joseph Beuys installation here - we have a fantastic one that we're never able to show. It is a cone made of cast mud that comes down from the ceiling." The last part of the building that we visit is the glass box on the roof. This long, bright room will be a restaurant, and it has the most dazzling views on all sides, including the northern side of the Thames, with St Paul's sitting plumply in the middle of the city. …