The N206 Ir. G. Tjalmaweg is part of the RijnlandRoute. The RijnlandRoute is a new road link between Katwijk, via the A44, and the A4 near Leiden. The existing route between Leiden and Katwijk has been doubled and built half sunken. This includes two flyovers and a new Torenvliet bridge built next to the existing bridge. The N206 traverses a landscape of beach ridges, beach plains, ancient river courses, crossing the LIMES, once the northern border of the Roman Empire.

What makes this project special is maximum commitment to the spatial quality of both the landscape and the artworks. In this respect, the road is subordinate to the landscape. The accompanying park strips form a high-quality green corridor between Valkenburg’s current residential area and the future development of Valkenhorst. The road itself is accompanied on its flanks by a 3½-kilometre wooden slatted wall that flows seamlessly into uniformly shaped noise barriers, overgrown with a diverse mixture of 38,000 climbing and bordering plants. This provides a varied image in both summer and winter. The sun and shade sides of the sunken Tjalmaweg have also been taken into account when applying the planting. This gives the N206 a natural green look and promotes biodiversity.

The park strips on both sides of the road extend into the road, even into the sunken position. In the long park zone on the north side, cyclists, walkers and playing children find their place within a high-quality continuous landscape. High-quality because of the large number of diverse types of users, but also because of the investment in mature plants, sustainable paving and furniture we designed. The undulating lines of bank lines, planting strips and walking and cycling paths express movement and emphasise the longitudinal direction of the park strip. Different user speeds are carefully separated and are designed to create a safe situation for all users.


The project approach, by shaping not only the road but also the adjacent landscape in an attractive way, was appreciated by the surrounding area.
An interactive participation process with local residents produced an adapted design for the park zone. Where a sustainable and safe walking path was designed for the elderly, children follow an adventurous route with a wooden play trail and stepping stones in the water.

Sustainable development

What makes the incorporation of this road unique is its sustainable development. Foil rather than concrete was used to create the ‘sunken box’, saving a large amount of concrete. The wood of the slatted wall comes from sustainable fast-growing European softwood which has been thermally modified. Element paving was reused in the design of the outdoor space. A large Wadi filters the water coming from the road and all the greenery along the walls is supplied with water by a trickle water system instead of rich (costly) irrigation.

An inviting place to stay

The space under the bridges is now laid out as an inviting residential area clad in cobblestones in a composition of narrow lanes and wider (parking) bays. On the Katwijk side, a platform has been placed in the water for fishing. There are seating areas at different heights on both banks. The design takes into account accessibility, walking routes, visibility and social safety. Here and there, higher platforms of anthracite-grey concrete tiles have been placed. These plateaus not only serve as seating, but are also there to keep out cars. The furniture with matching lighting adds utility value to the space under the bridge and thus increases social safety. The bats present have been taken into account by not shining any light on the water.

Roman past liveable

Parts of the foundation of the Roman road were actually found during the first preparatory excavations. These historical finds were integrated into the design in several ways: in the cycle route along the N206, in the walls of the sunken section and in the naming of the viaduct. A section of the Roman road has been reconstructed on the original alignment. Exactly what the road looked like is difficult to determine, as only the foundation of the road was found. Together with an archaeologist, the structure of the foundation, which originally consisted of oak posts, was brought back to life. This spot, shielded from car traffic, offers the chance to rest for a while and reflect on the landscape and its history, thanks to an information board and the replica of the border road.


While relieving traffic congestion and improving the region’s accessibility, the road does so with respect for the past. The green park strips, the dwelling places under the Torenvliet Bridge and the visible remains of the Limes not only offer better liveability, but also pay homage to Roman heritage. In its role as a traffic artery, the N206 Ir. G. Tjalmaweg not only relieves the region’s traffic congestion and accessibility, but also provides a green connection to the Roman past.

Client: Boskalis Nederland, Province of South Holland
Other landscape architecture offices involved in the design of landscape: –
Architecture offices involved in the design: architect ZJA
Location: 52.176187616851834, 4.433132984834762 (between Katwijk and Leiden)
Design year: 2019 – 2023
Year Completed: 2023


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