As an expression of sustainable architecture – a central theme of the Expo – the pavilion was constructed with recycled materials that can be dismantled and used again. Over the main hall is a lattice-grid shell of cardboard tubes. The end walls are in a cable-tensioned cardboard honeycomb construction, while the roof skin consists of a five-layer fire- and waterproof paper membrane. Even the sand-filled steel foundations can be removed and used again later. Extensive trials were necessary to obtain planning approval, however. The structure had to be reinforced with curved timber ladder girders, which, together with the steel stays, form the real load-bearing elements; and the paper membrane had to be covered with an additional PVC fabric.