Clockwork carnival: mixing the atmosphere of a fete d'ete with concerns about the Swiss place in the world, Switzerland's Expo is choreographed around a set of iconic modern follies.

'Switzerland,' observed Hemingway somewhat testily in 1922, 'is a small steep country, much more up than down than sideways, and is stuck over with large brown hotels built in the cuckoo-clock style of architecture.' Alpine trimness and smugness often seem to bring out the worst in visitors, but mindful of their reputation for slightly sinister insularity, the Swiss are anxious to challenge such preconceptions. Currently unfolding with great ceremony on a quartet of lakeside sites, the sixth national Swiss Expo is conceived as an all-singing, all-dancing microcosm of the Swiss knack of efficiently taming and unifying geopolitical diversity. Costing almost as much as the UK's Millennium Dome (and not without its own attendant controversies over timing, content and finance), the [pounds sterling]600 million Expo ambitiously encompasses five cantons, three lakes, two languages, four towns (Yverdon-les-Bains, Neuchatel, Bienne and Morat) and 8000 staff plus a glossy posse of foreign architects.

Despite a growing view that the Expo concept has become an overblown and unmanageable irrelevance, the Swiss still seem to consider it worth the energy and expense. Expense has been an issue -- two thirds of the funding came from the public purse, but the project has been dogged by delays and cost overruns and finally opened a year later than planned. Estimates suggest that it will need 10 million visitors to break even, twice as many as are realistically anticipated. Yet the Swiss have had a long and apparently cherished relationship with their Expos, which have historically served to reinforce connections between different cultures in a strongly decentralized country. Switzerland's first National Exhibition, held in Zurich in 1883, brought together manufacturers, producers and industrialists from its assorted cantons, while the 1939 Expo (also in Zurich) proved a popular and effective means of strengthening a sense of national identity on the eve of the Second World War.

The aims of the Expo 2002 are more diffuse and less trade-oriented, but like its predecessors, it provides a snapshot of a society trying to reconcile its internal peculiarities with how it is perceived by the outside world. However, while Seville (AR June 1992) and Lisbon (AR July 1998) were catalysts for major urban development and the transformation of derelict and de-industrialized sites to new productive uses, Switzerland seems to have no such wider agenda. The chosen setting is the Three Lakes (a north-west, French-speaking region famous for its wine and watchmaking), which is relatively prosperous and squeakily clean, with few of the environmental and social problems that beset larger urban or industrial centres. Its picture-postcard landscape makes it the perfect bucolic backdrop for what is essentially a Swiss fete d'ete, a bright, transient summer circus of diversions and entertainments, carefully choreographed by a cast of architects, landscape consultants and interior and exhibition designers. The various sites or arteplages ('beaches of art') are linked by pleasure cruisers that ply their leisurely way around a network of lakes and rivers, reinforcing the air of seasonal jollity. (A fifth mobile arteplage takes the form of a converted boat.) Come the end of October the tents will be folded, the amusements disappear and Expo will simply evaporate. Somewhat astonishingly, there are no wider plans to develop the arteplage sites on a more permanent basis, for instance as lakeside parks, so there will be no lasting physical legacy.

In logistical terms, distributing events over four centres does makes Switzerland's Expo a more manageable and enjoyable proposition for visitors -- both Hanover (AR September 2000) and Seville were characterized by lengthy trudges around vast trade fair complexes. Each of the four sites connects town with lakeside and each boasts an offshore iconic showpiece (or 'forum') designed by a star architect, which serves as an instantly memorable image, a kind of avant-garde branding. The range of imported architects has given rise to some intriguing formal diversity: Diller and Scofidio's ephemeral vapour cloud at Yverdon-les-Bains is the polar opposite of Jean Nouvel's enigmatic, rusting monolith that brings a whiff of Space Odyssey to the little historic town of Morat. At Bienne, Coop Himmelb(I)au have devised an array of dislocated sculptural towers that resemble broken chess pieces, while in Neuchatel Groupe Multipack (a collaboration involving both French and local firms and perhaps the least successful of the iconic quartet) resort to flying saucers on stilts surrounded by a field of rippling polycarbonate reeds. These four interventions are considered in more detail in the following pages.

Each site is allotted a portentous-sounding dualistic theme ('Power and Freedom'; 'The Universe and Me') that loosely yokes together the smaller-scale attractions, experiences and fairground rides that cluster along each waterside in specially landscaped 'expoparks'. Despite being temporary, the level of planning and landscaping (especially at Yverdon-les-Bains, where West 8 have created an undulating panorama of hollow hills) is generally imaginative and, as might be expected, everything is very well made: even minor ancillary structures manifest a reassuring Swiss precision and attention to detail. Some of the exhibition tableaux hint at an underlying angst about issues such as nationalism, a sense of identity, cultural stereotypes, the Swiss place in the world and the world's view of the Swiss, but the pervading impression is of a carnival run like clockwork, a contradiction that could perhaps only take place in Switzerland.

Swiss National Exhibitions, until 20 October. www.expo.02.ch