Lookout Tower in Helsinki Zoo

The tower was the outcome of an international student competition and was to stand in a prominent position high above the sea. The prizewinners justified the free curves of their design by arguing that they had a greater affinity to man and nature and were more economical than rectilinear forms. In order to avoid problems in implementing the scheme, there was a protracted trial phase, with 3-D simulations and models. The finely articulated, self-supporting net-like structure of the tower consists of 72 curved wood strips. After extensive tests, it was decided to have these 6 ? 6 cm laminated members bent to seven different radii at works and to shape them to their final curvature by steam treatment on site. The members were simply bolted together and braced in part with nailed plates. To stress the transparency of the outer skin, the internal platforms and stairs were executed in solid laminated timber, thereby forming independent spatial entities within the overall tower space. The timber members were treated with linseed oil as the sole form of protection.