A new observation tower of COR-TEN steel and locally-sourced timber blends in with the tree canopy and links to a treetop walk with views over Zealand

At Denmark’s biggest treetop adventure park, visitors will soon enjoy views stretching 25 kilometres from a point 45 metres above the ground.

The hyperbolic observation tower is a new structure at Camp Adventure Park, which is located in Gisselfeld Klosters Skove, a protected forest an hour’s drive south of Copenhagen.

It is designed by Danish architects Effekt, who worked with the engineering firm Arup. “First of all, we chose the best spot in the forest to preserve as many trees as possible,” explains Effekt’s project architect Toni Rubio Soler.

“If COR-TEN steel had existed at the time of the building the Eiffel Tower, Paris would have saved more than eight tonnes of paint a year.”

Toni Rubio Soler, Effekt

And rather than adopting the standard cylindrical shape for observation towers, the architects configured an hour-glass form, which makes the structure stable and increases the size of the viewing deck at the same time. “The hyperbolic shape of the tower also leaves space for the tree canopy, where the structure is most slender, while letting you get very close to it,” adds Rubio Soler.

The tower houses a 600-metre-long internal ramp that keeps a fixed gradient as it winds up from the forest floor. This gentle route makes the tower and the 900-metre-long treetop walkthrough canopy accessible to everyone.



Given its forest setting, the architect initially considered using wood for the tower’s structural elements. “But the construction of a wooden tower of such a height (45 metres) is simply not viable,” says Rubio Soler. However, wood from the surrounding forest is used for the surface of the boardwalk and the ramp.

Instead, Rubio Soler specified COR-TEN steel. Although it was more expensive than painted standard steel, “in the long run it’s cost-efficient as it is a maintenance-free material,” he says.

COR-TEN steel, also known as weathering steel, is formed from a set of alloys originally developed by US Steel to remove the need for painting. After prolonged exposure to the environment, a stable rust layer forms that protects the unoxidised steel structure underneath. This process can take up to six months if left to occur naturally, but there are processes that can speed this up significantly.

“We told the client that if COR-TEN steel had existed at the time of the building the Eiffel Tower, Paris would have saved more than eight tonnes of paint a year, and he was instantly convinced.” Aesthetics were also a consideration. “The beauty of COR-TEN steel in a forest is that it blends perfectly with the surroundings, and appears as a natural material,” he adds.

The delivery time for such large amounts of COR-TEN steel, which was supplied by Sanistål, is longer than for regular steel, and this resulted in a slightly longer construction process. However, this was accounted for in the planning of the construction.

Rising 135 metres above sea level, Effekt’s tower will be the highest accessible spot in the entire region of Zealand when it opens in autumn 2018, offering beautiful views and a unique style.


Images: © EFFEKT Arkitekter, Camp Adventure