Kupla - Helsinki Zoo Lookout Tower | The Metamodern Architect

Kupla – Helsinki Zoo Lookout Tower

In a world where rectangular forms are considered the norm, this wooden observation tower in Helsinki, Finland, begs to differ.

Named after the Finnish word for the bubble, the Kupla – Helsinki Zoo Lookout Tower is a ten-meter wooden lattice structure perched atop an 18-meter high cliff. This 82-sqm pavilion offers panoramic views of the sea and the surrounding city of Helsinki, serving as a delicately transparent landmark for the Korkeasaari Island.

The whole project commenced in 1999 when Wood Focus Finland and Korkeasaari Zoo launched an architectural competition for the architecture students of the Helsinki University of Technology. Its draft design was conceived by students of the multi-national Wood Studio Workshop, which are then completed through an arranged workshop between 2000 and 2002.

According to Ville Hara, designer of the winning entry and now the co-owner of Avanto Architects, the abundance of curvilinear forms in nature inspired him to mimic a grid shell structure that follows the existing low stone wall and wraps around a small birch grove. Diving into the psychology of its organic form, its likeness to the human physique creates an emotional connection to the users, recognizing this form as humane. Furthermore, the usage of similarly vaulted geometry has also been proven to be durable and cost-effective, which made it an architectural staple throughout history.

The entire structure rests on a concealed reinforced concrete foundation via customized steel joints. Its irregularly-shaped wooden lattice shell was made possible through the assembly of 72, 12-meter long, glue-laminated battens. Although these battens were already factory bent into seven various preformed shapes, achieving the structure’s desired geometry required these battens to be further bent and twisted during the construction process. To form its wooden space truss, members are connected with double-sided nail plates and 10-mm through-bolts – altogether forming more than 600 joints in the tower.

Visitors are welcomed with a steel-framed opening leading to a series of wooden stairs. Inside, its two elliptical floor levels are supported by edge beams at their perimeters, which are then connected to the truss by deck bolts. These bolts were responsible for providing the structure’s needed horizontal stiffness and support to the lattice members.

The open-air nature of the structure made no room for any structural protection against weathering. Hence, the solution involved treating its wooden members with a linen oil-based wood balm equipped with UV-protecting capabilities.

Decades after the completion of the Kupla – Helsinki Zoo Lookout Tower, the structure persisted on its towering glory, a tangible reminder of an intangible bond between architecture and human nature.