MORAL MAZE.

The swiss pavilion is a triumph of metaphor and abstraction largely because it, and its contents, were orchestrated by Peter Zumthor without an exhibition designer fighting against the architect's intentions.

From his earliest years, Peter Zumthor has been involved with wood. Son of a furniture manufacturer and trained initially as a cabinet maker, he was brought up with its smell in his nostrils, and its potential at the end of his fingers. The first buildings which brought him international attention were made of timber: the little chapel at Sogn Benedetg and the Roman museum in Chur (AR January 991), where he explored the acoustic, luminous and aromatic properties of the material with exquisite sensitivity.

Now, he has made the Swiss pavilion in Hanover, and has used much of his previous experience to make an unforgettable, calm, yet rather disturbing presence, which is perhaps the most potent in the whole of Expo. It is a timber labyrinth. Bearing in mind the principles behind the Hanover exhibition, its wooden walls are held together without nails, screws or glue, so that at the end of Expo, they can be sold off (or re-used). Long thick horizontal planks of ruddy pine are separated by pale square larch cross-members. Everything is held together by stainless-steel rods in tension quite highly stressed by springs to form in compression what Zumthor calls a 'wood yard'. It may be the most elegant and sophisticated wood yard in the world, but its three-dimensional lattice structure will work excellently as a timber seasoning device.

During the course of the exhibition, the height of the structure is expected to shrink by about 120mm as the timber dries out and is compressed under the effect of the springs, which will gradually reduce their tension as the walls contract. Sometimes the pine weeps sticky, sharp-scented tears of resin as the wood is gradually transformed. Zumthor is prepared for the possibility that during the pavilion's life, whole walls may deform and buckle. He wants them to move. They will add to the organic resonance of the place or, if any become seriously deranged, they will be adjusted. Constant supervision will be needed and corrective measures taken: a metaphor perhaps for the nature of Swiss society.

Zumthor calls his building a Klangkorper, a sounding body, because rain on the wide galvanized gutters which form the roof turns it into a huge musical instrument, played on by God and Nature. But there are other sounds in the place as well. Zumthor, who won the project in competition, presented a scheme which is intended to appeal to all the senses, not only in its physical presence, but with contributions from other artists, musicians, writers, theatre workers, culinary experts, all conducted by the architect. One of the initial ideas was that the place should be a sort of 'rest house', where people could relax in the small internal piazzas to which the maze (without too much difficulty) delivers you -- or in the strange black oval three-storey elements which house the service parts of the pavilion, and have quiet spaces on top with Jacobsen chairs. Though Zumthor vigorously denies that there is anything in the place which is obviously intended to evoke Switzerland, here is again a trace of one of the esse nces of the country, the tradition of efficient, soothing hospitality.

Unlike many of the national pavilions, the Swiss one is entirely funded by the federal government, so there are no sponsors whose wares have to be displayed, garishly and crudely competing with the pavilion itself. It evokes the notion of a decent, complex, subtle society, with gentle musical sounds, the scents of delicious food and drink mingled with the aromas of wood, the words (in Switzerland's many languages) projected fleetingly onto the walls, or engraved on them, the strange little performances in the courts. Physically subtle too, because the walls are both opaque and permeable: as you walk down the paths of the maze, they seem almost solid, and directive. But turn straight onto the walls, and you can see through the slits. And see strangely edited versions of people's figures and faces: individuals glimpsed intensely in the strange little city of sensations which has been made with such elemental means.