Building up your inner child

There is something inherently absurd about an architecture gallery - an Alice in Wonderland sensation that some basic rule of hierarchy has been up-ended. A room is inside a building, after all; a building is not inside a room. And yet if such a gallery is to work at all, it has to find some way of overturning that statement of the obvious.

There is something inherently absurd about an architecture gallery - an Alice in Wonderland sensation that some basic rule of hierarchy has been up-ended. A room is inside a building, after all; a building is not inside a room. And yet if such a gallery is to work at all, it has to find some way of overturning that statement of the obvious.

There are other problems, too. Architecture is an art of enveloping space, not just façades and elevations, and yet there is only one interior available to the curator - that of the gallery itself. And while there are actually museums that collect buildings (The Museum of Welsh Life, near Cardiff, is one example, with some 30 buildings on a 100-acre site), that is hardly an option for the Victoria and Albert Museum, whose new architecture gallery has to find space for the Hagia Sophia, St Paul's Cathedral and Norman Foster's Gherkin, among many others.

Fortunately, that is a problem architects have already thought about from another perspective - since they're in the business of selling people something very expensive that doesn't actually exist. It's not entirely surprising, then, that the V&A and Riba Architecture Gallery should resort almost entirely to the solutions architects have already devised for bridging the awkward gap between conception and reality - that is, drawings and models. A drawing is pretty much the first thing you see when you enter the gallery: a huge isometric projection of St Paul's Cathedral, strategically cut away so that you can see how Sir Christopher Wren's monumental confidence trick functions. It's like a giant Dorling Kindersley illustration - with less colour, perhaps, but with no less childlike pleasure in explication - and it proves a fitting introduction to an exhibition space that is unusually satisfying to the child within.

A lot of things don't quite work here. The thematic arrangement of the gallery seems at once over-complicated and simplistic; I suspect most visitors will abandon it pretty quickly and just browse. The drawers that line both sides of the room, and house a selection from Riba's fantastic collection of architects' drawings, initially strike you as a good idea - until, that is, they strike you for real. Since they are engineered like a Rolls-Royce door and are five or six feet wide, like the blueprint drawers in an architect's office, pulling them out when the gallery is crowded involves applying for formal planning consent from your neighbours on both sides. And if you happen to catch a Frank Lloyd Wright frontal elevation in the shins, believe me, it leaves an impression on you.

A lot of things do work, though; and the models are foremost among them, from a contemporary wooden miniature of St Martin-in-the-Fields to a three-dimensional rendering of Fort William in Calcutta, crafted from ivory, silver and wood. These are perceptual tools - little devices that enable you to get a firmer grip on how a building will mark a skyline or make a pattern on the ground. But they feel more like toys as you look at them - and the fascination they induce is not at all intellectual. It's about mastery, not just in the sense that they're often beautifully constructed but also because they shrink complexity until it is graspable.

Sometimes, that is literally true - one case in the V&A gallery includes three small models of the structural joints for Richard Roger's Stansted airport building, and though you can't touch them, you know that they are intended to be turned over in someone's hands, to show how the elements interlock. In other cases, it's simply a matter of making you feel bigger than you are. You can't look at a model of a building without imagining yourself walking through its doors or wandering along its parapets, and that in turn gives you an exhilarating feeling of stature. Only a giant could get such a view.

It is all delightfully reminiscent of the playroom - and it prompts the thought that, although it is in some respects the most grown-up of the plastic arts (because it so directly affects people's lives), architecture is also the most in touch with a child's imagination - with their pleasure in manipulating imaginary worlds. This seems to be confirmed by one of the more modest projects on show, a proposal for a Courtyard House by Patrick Gwynne, which was never actually built but is represented here by the original model. This was originally constructed with an inbuilt electric motor, so that the circular roofs would rise like a set of cocktail umbrellas at the flick of a switch, exposing the detailed modelling of the interior. Why an electric motor? Because no child could resist the Thunderbirds touch - and even the most serious architects are children at heart.