Dan Graham makes jokes about the least funny thing in the world - architecture. He discombobulates, an artist-parodist whose parodies teeter close to the real thing. His proposals for pavilions that distort, multiply, invert and mess with our conception of social space seem ever more likely to influence real architecture in the real world.
In this show of recent plans, models, photographs, videos and, most enjoyably, two actual pavilions, he teases us into seeing more sharply. Your own image pursues you threateningly through the gallery, reflected in dark smoked glass, a hexagon of mirrors. You turn a corner, and come bang up against yourself again.
Graham leads you into a palace of illusion in which the depth of spaces is as hard to gauge as your own position in the maze. Whether walking through the mirrored multiplicity of the Greek Cross Pavilion or pacing around the Triangular Pavilion With Circular Cut-Out Variation, you are confounded.
Graham has always been an entertainer. On video, he lectures in an obsessive manner to a group of baffled, giggling students in the 1970s. His debut was a deadpan commentary on the deadening architecture of modern suburbia, published in an art magazine in 1966.
Homes for America was an uninflected presentation of photographs of cheap housing that pointed out the grid-like layout and repetitive forms of the average housing estate - a satirical swipe at minimalism, the dominant art movement of the day, which delighted in such regularities, repetitions and mass-produced building blocks.
Graham pointed out the similarity - monotonous regularity - between the avant-garde strategy and mass-produced vernacular building.
He has spent the rest of his career interrupting regularity, turning the rational, box-like restrictions of modern life on their heads. Or rather, on their sides. He looks not for an antithesis of modern rationality, but for its own secret madness.
What could be more sensible than combining a fish tank and swimming pool, as he proposes in a model that divides people and their fishy friends by a transparent partition? I also like his proposal for a designer clothing boutique in which anamorphic projections confront visitors with fat and thin versions of themselves.
His architectural proposals are reasonable, practical, buildable. They just give things a slight twist, so that the logical becomes nutty and we're pleasantly lost in the fun house.
• Until September 14. Details: 020-7724 2739.