Dutch architects UNStudio have designed a concrete observation tower to cantilever into the sky above a nature reserve in the Netherlands.

The 25 metre-high tower will be primarily constructed from a high-performance concrete that the studio has been researching alongside engineers ABT, developer BAM Utiliteitsbouw and concrete manufacturer Haitsma Beton.

This dense concrete strengthened by steel fibres will enable the impressive cantilever, while embedded steel members will provide additional stability.

Visitors will climb 134 steps to reach the highest of the tower’s three viewing platforms, which will be positioned five metres above the surrounding forest canopy.

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A steel mesh parapet will create a balustrade for the staircase and platforms.

We've featured a few observation decks and lookout towers on Dezeen - see more here, including a tower with shipping containers on top.

Other projects by UNStudio on Dezeen include a pavilion in New York's Battery Park and an installation in an abandoned fort - see all the projects here.

Here's a project description from UNStudio:

UNStudio’s design for an Observation Tower for ‘De Onlanden’ presented to Natuurmonumenten

On September 22nd the design for an observation tower for the nature reserve ‘De Onlanden’, situated to the South-West of the City of Groningen, was presented to Natuurmonumenten (the Dutch Society for the Preservation of Natural Heritage) during the mini-symposium ‘Experience Nature with innovative concrete’ in Peize. The observation tower is the result of a study into the optimal application of Ultra High Performance Concrete by a case study team comprising of UNStudio, ABT, BAM Utiliteitsbouw en Haitsma Beton. Natuurmonumenten received the design as a gift from the case study team.

Case Study Observation Tower Ultra High performance Concrete

The design for the observation tower is the result of a case study which aimed to apply the characteristics of Ultra High Performance Concrete in a functional, operative design. The case study team consisted of designers, engineers and builders who together sought a solution through which architecture and construction could reinforce one another. According to Ben van Berkel, “The observation tower afforded our Inventive Materials Research Platform the opportunity to investigate the properties of Ultra High Performance Concrete and to truly test out the full potential of this new material in a real structure.” Ultra High performance Concrete differs from normal concrete as it has a very high density, contains steel fibres and has an extremely fine grain structure. These properties facilitate the application of large compressive stresses in structures of narrow dimensions. UNStudio’s Inventive Materials Platform is one of four in-house research platforms and aims to investigate custom-made material applications and to facilitate inspired and imaginative collaborations with other experts and with manufacturers in the construction industry.

The Observation Tower

The 25 metre high observation tower will be realised on the forested boundary of ‘De Onlanden’ nature reserve on the outskirts of Groningen. Once built, the tower will extend 5 metres above the trees and will offer views over the 3,000 hectares of natural landscape which form the largest water storage area in the Netherlands.

The design for the observation tower guides visitors in a fluid ascent up the 134 steps to the highest viewing point. Visitors are lead via the first set of steps to the lower viewing platform which stands at a height of 10 metres. Following this, the second set of steps provides a turn in direction, allowing for an alternative view of the surrounding forested pastures. These steps lead visitors through the tree tops to the second viewing platform which stands at a height of 20 metres and offers views over the nature reserve around the city of Groningen. The highest viewing platform, at a height of 24 metres, is reached via the final set of steps and offers visitors a wide open vista of ‘De Onlanden’ nature reserve.

By means of changes in direction in the structure of the observation tower, visitors can experience views of the surrounding natural landscape from different perspectives, whereby the height of each viewing platform offers a different experience of the vistas over the surrounding landscape. From the highest viewing platform views are afforded of the Groningen skyline, which includes the Education Executive Agency & Tax office building which was also designed by UNStudio.

Ben van Berkel: “The Netherlands enjoys a rich and textured natural landscape, but unfortunately the Dutch topography is not very varied; we don’t have mountain ranges, or many hilly areas from which to enjoy a panoramic overview of our natural surroundings. The viewing tower for ‘De Onlanden’ was designed to provide the opportunity to create a new awareness and different perspectives of the landscape we move through, but may otherwise never experience in all its scope.”

The fine lines and the form of the tower bring to mind the silhouette of a deer. UNStudio’s design has therefore been given the (provisional) name ‘Het Hoge Hert’ (The Tall Stag).

The observation Tower is a hybrid construction, consisting of a combination of steel and Ultra High Performance Concrete. Steel is employed where the tensile stresses are foremost, whereas Ultra High Performance Concrete manifests excellent performance properties where the compressive stresses are highest. The parapet around the stairs and platforms is constructed from stainless steel mesh, enabling the combination of both maximum transparency and necessary safety levels.
Ben van Berkel: “The strength of Ultra High Performance Concrete is conceptually expressed in the cantilever of the structure, which combines UHPC with steel to enable a substantial protraction in the form of the viewing tower.”

Client: Natuurmonumenten
Location: Outskirts of Drenthe (near City of Groningen, Eelde and Peize)
Height: 25 m
No. of steps: 134
Programme: Observation Tower
Status: design

UNStudio: Ben van Berkel with Arjan Dingsté and Marianthi Tatari, Marc Hoppermann, Kristoph Nowak, Tomas Mokry, Dorus Faber

Case Study partners: UNStudio, ABT, Haitsma Beton, BAM Utiliteitsbouw