At the entrance to the gallery you're asked to put plastic bags over your shoes, in order to tiptoe without trace past white surgical curtains screening off spaces where - you imagine - unconscious patients lie. But this is not simply a spectacle; you too are invited to lie down. There are cubicles curtained off and facing out on to Kensington Gardens, each containing a bed that looks more like a sarcophagus: a monumental slab on whose inclined surface you lie like a corpse in state, observing the walkers in the wintry park. This sepulchral quality intensifies in the central hall, where there are little dream houses like tombs. Shut the door and the outside world is lost: you are isolated inside a tiny bedroom where coloured palm trees and stars are projected in the darkness. Someone opens the door and gasps. "I thought you were a body ... "
The Kabakovs' installation is not a random collection of spaces but an architectural concept. As you enter, there is a wooden model of The House of Dreams as it would appear if it were fully realised. This utopian rotunda is only partially carried out in the installation, and yet the gap between plan and practice is significant - all utopias fail.
It's distinctively Russian. The labyrinthine succession of little chambers and screened corridors resembles the interior of St Basil's church in Moscow, or, in its whiteness, the space station in Tarkovsky's film Solaris.
As you lie on your slab, the style of this fictional place - from the surgical curtains, which belong in some Soviet sanatorium, to the neoclassical Stalinist architect's model and, most of all, the white tombs - makes you realise that you are not just any dreamer, paralysed while a world beyond your control or understanding glides by. You have become Lenin, sleepless in his mausoleum, tormented by incomprehensible voices of the 21st century.
· Until January 8.Details: 020-7402 6075.
