The wooden observation tower Kupla is located in Korkeasaari Zoo. The site is situated on a cliff-top, eighteen meters above the sea-level making the whole spot very visible in the Helsinki sea line. The ten-meter lookout tower has become a landmark for the Korkeasaari island.

The whole project started in 1999 when Korkeasaari Zoo and Wood Focus Finland launched an architectural competition for the students of architecture at Helsinki University of Technology (Aalto University). The winning entry was designed by Ville Hara, nowadays a co-owner of Avanto Architects. The draft design was developed by a group of multi-national Wood Studio Workshop students. The workshop was arranged between 2000 and 2002 and the project was completed during this period.

The design of the tower was inspired by the natural context of the construction site. The free form follows the surrounding low stone wall and skirts around a small birch grove. The organic shape was intended to be both individual and structurally feasible.

The load-bearing grid shell structure consists of 72 glulam battens bent and twisted on-site from seven preformed types. Over 600 bolted joints hold the strong but light meshed shell structure together. The structure reminds an eggshell; even when the grid shell is punctured, it withstands the load. As the tower has no structural protection against the weather, it is treated with a linseed oil-based wood balm with UV-protection.

The Finnish word Kupla means a bubble in English. Ville Hara has explained that the shape was chosen because curvilinear forms are present comprehensively everywhere in nature. This kind of forms are also closer to human physique, which is why people experience organic forms as humane. The vault shape structures are also cost-effective and durable and have been used throughout the history.