Icoon Terneuzen

De Wervel (The Swirl) is our entry for ICOON, a competition to design a tower for the city of Terneuzen. The design was parametrically generated and structurally optimized to weigh only 18 tonnes, using old gas pipelines for its steel structure. A co-creative phase with local residents, led to many references to the watertower that was demolished in 2000. Our tower pays homage to that one, with a literal modern twist, and using contemporary and sustainable materials. Summum Engineering carried out the entire design, modelling and engineering.

De Wervel is characterized by a robust, structural shape, which is mainly intended to be as high as possible but using as little material as possible. The optimized steel structure is lightweight compared to other towers of similar height. Its viewing platform is accentuated by four rings, which are a nod to the design of the old water tower by Arie Jan van Eck. This tower once stood nearby and is still loved and fondly remembered by Terneuzen’s citizens.


Walking over the dike you slowly approach the twisting shape that emerges from the water like a maelstrom. Once you arrive, the entrance to the basement unfolds.

As you take the steps and ramps down, you descend into the dike itself. The retaining walls show high water levels with their flooding probabilities, for example “+5.40m NAP, 1x per 1,000 years”, but also “+4.96m NAP, 1 Februari 1953”, the date of the infamous North Sea flood.

The retaining walls work as windbreaks and together form a suntrap. The zigzagging ramps for the disabled create, along with the stairs and walls, an amphitheater. This open-air theater offers performances, for example during ZeelandJazz and the Havendagen Terneuzen, and could be operated by the nearby Scheldetheater.


Once inside you first enter the darkness of the round basement. The cylindrical cellar is a 35m long, 4m high panorama, as in the 19th century tradition of Panorama Mesdag or, more recently and closer, Panorama Walcheren. Zeeland has panoramas from the latter that need a new home, but also a renowned graffiti artist of murals, or co-creative paintings. In each of these options, places and moments are immortalized. A more versatile, but also more ambitious version of this idea is a 360° panorama projection with sound and bilingual voiceover. Many views could then be shown: live views from the top of the tower, time‐lapse images over the whole year, imaginary views from the past, or from completely different places and towers in Zeeland, the Netherlands, Europe, the whole world or even beyond. The nearby CineCity could operate this panoramic cinema.


A spiral staircase takes you from the dark below into the light of the tower’s atrium above. Inside the atrium, the balcony, spiral staircase and climbing nets – with their materials from naval tradition – catch the eye. A double handrail (one for adults and one for children) takes you up the stairs, where there are two levels of rope nets. These function as playful objects and at the same time as a fall protection.

The spiral stairs directly run along an open fabric facade. Although this sail-like cladding offers protection and creates an indoor climate, it still lets you feel and experience the elements.

Once a year, the atrium also serves as an exhibition space as well as information and starting point for the Beeldenroute that stretches along the Scheldeboulevard to the Vesalius statue.


Arriving at the top, you have a full view of the economic heart of the region, where seventy thousand ships pass on a daily basis. You see the locks, the industry, the city center, and also the Waterfront residential towers, where the old water tower once stood. The platform has stands that are covered in case of poor weather or bright sunlight, and has a number of bilingual information signs regarding the city, the surrounding area and the tower itself.

The signs feature QR codes that lead you to (existing) websites with more visitor information about the surrounding attractions. But also to current information for shipspotters: passing ships – what are their names, where do they come from, where are they headed – the weather, the tides and water levels, and the position of the stars and planets. In a far-reaching variation of this concept, the QR codes lead you to an app or platform in which this data is stored collected and made transparent. This can be done by means of an online interactive map or even via your camera with augmented reality (AR) layers superimposed on your camera view.


The shape of the tower is made up of two minimal surfaces: a catenoid and a helicoid, which form the facade and spiral staircase. The walkable helicoid is like an upright ship propeller. The sail follows the catenoid, a shape that resembles many a water tower, such as the one in Oostburg, also by Van Eck.

The spiral staircase follows a spiral that has been optimized according to the Dutch building code. The angle of the stairs is therefore always between 30° and 45° with a platform every four meters. You can easily pass each other on this wide staircase.

The shape of De Wervel was generated by running through countless variations in a parametric optimization model. The model starts with an initial spiral. As mentioned, the spiral is such that the in- and outside of the corresponding staircase will always follow the allowable angles, for optimum comfort. This spiral is copied around the central axis of the tower, and intersected to form a grid. The surface shape can be varied to find the least amount of steel needed to resist wind and user loads. At regular intervals, platforms allow for views and access to climbable rope nets, suspended within the tower’s atrium.


The substructure of the tower consists of a concrete basement with a pile foundation and retaining walls, made from low-carbon and recycled concrete. The dike revetment of basalt stone and grass vegetation is the same as the rest of the dike. As a result, the base of the tower blends into its surroundings, and the experience of descending into the dike is enhanced. The street lighting, paving and retaining walls also make the same use of materials as elsewhere in the Veerhaven.

The tower itself consists of materials associated with ancient and modern shipbuilding: sail for the facade, which partially shields the structure from the weather; rope for the climbing nets; modified wood or wood from reused bollards for the floors and steps, referring to a ship’s deck; and, steel for the circular hollow steel structure, made of former gas pipelines that are given a second life here. The high degree of sustainability and circular use of materials turns De Wervel into a demonstrator and pilot project for construction innovation.


The jury thought our submission was complete, clearly structured and well described, with very sustainable and circular materialization. The design was ultimately deemed not unique enough to be selected. Find out more about the competition on the website of ICOON.


Project team
Shasan Chokshi, Diederik Veenendaal, Niels Hofstee | Summum Engineering
Viera Kudivani, Frantisek Kudivani | Pictown (renders)
Reno Maenhout | Photo Inhorus (drone photography)

Charl Smit | Fraai Werk (lighting design)
Egon Bijlsma (dike construction)
Hans Laagland | Witteveen+Bos (general advice)
Simon Visser | Poly-Ned (membrane construction)
Mick de Haan | AIP partners (steel construction)

    Location: Terneuzen, Netherlands
    Time: 2021
    Status: Competition

    Services: Design, structural engineering, parametric modelling


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