The use of the areas either for their construction and their dismantle was of two years, while the exposition itself lasted from May to November 2002; there has been therefore the necessity to use large areas for a short time. We have tried to minimise the environmental impact due to the occupation of common existing areas, though temporary, which could create few problems to the already difficult balance of the modern cities. This problem has been solved by using exposition areas on the lake by building great platforms on wooden foundation piles.