The Bords de Seine project will reinvent the Terrasses 3-5 and Echangeur sites and create new links between La Défense and Nanterre.

The Seine River and Mont-Valérien were decisive factors in the settlement of the first populations in Nanterre. This site, with its exceptional geography, has seen a succession of major infrastructure projects, particularly in the 20th century, which overlooked the specific characteristics of these places and their populations, resulting in numerous brownfield sites that have served as both barriers and opportunities for the emergence of several initiatives. Today, the area reconciles the heritage of the historic axis with the new raison d'être of Europe's leading business district.

As an integral part of the Seine-Arche ZAC (joint development zone), the Bords de Seine form a complex perimeter covering three main sites:

• République-Université, from the university to the Anatole France housing project,
• Terrasses 3-5, between Terrasses 7-17 (on the Grande Arche side) and the Chemin de l'Île departmental park,
• The A14/A86 interchange, which extends the Terrasses to the edge of the Chemin de l'Île departmental park.

A14, A86, slip roads, railway tracks, RER A viaducts...: in recent decades, the banks of the Seine have inherited numerous infrastructures that have shaped a highly contrasting landscape. Although the topography is made up of bridges, embankments, and other underpasses, a bucolic natural environment emerges upstream from the Seine and the Chemin de l'Île park.

Slightly offset from the historic axis, Terrasses 3-5 are its natural extension. Located between the RATP RER A tracks and Avenue de la République, Terrasses 3-5 take their name from the urban concept devised by urban planners Treuttel-Garcia-Treuttel when the Seine-Arche ZAC (joint development zone) was created. This public space consists of 17 landscaped terraces stretching from the Grande Arche de La Défense to the downstream loop of the Seine.

The site forms an unexpected green space within a dense urban fabric, despite the A14 motorway junction. The aim is therefore to reconnect this site to the surrounding neighborhoods and offer cultural and agricultural programming in line with the raison d'être of Paris La Défense. Established in 2008 on the Terrasses 3-5 site, the Paranda Oulam - La Ferme du Bonheur association has occupied this wasteland to carry out agricultural activities with vegetable gardens, enclosures (geese, pigs, sheep), beehives, and dry stone walls. The farm has practiced urban agriculture and slow soil decontamination, supported in particular by AgroParisTech.

Since 2024, the association “Le Parc Rural Expérimental” (The Experimental Rural Park), known as Le Pré, created by Patrick Bouchain, Grand Prix de l'Urbanisme, Bernard Latarjet, and Dominique Lemaistre, has been based on this site to consolidate its agro-pastoral, educational, and experimental research vocation and to prefigure the collegial programming approach to come.

The Terrasses 3-5 redevelopment project involves various stakeholders in the area to build a project that meets several objectives:

• Enhancing biodiversity: Terrasses 3-5 has a wealth of plant life and biodiversity that must be preserved and promoted. It is home to more than a third of Nanterre's biodiversity: woodlands, hedgerows, and meadows provide shelter and food for wildlife (insects, mammals, birds). As a biodiversity hub, it is a link in Nanterre's ecological network that the redevelopment project aims to strengthen.
• Improving accessibility: Between Rue Anatole France and Avenue de la République, a pedestrian and cycle path, known as the “lower link,” will cross Terrasses 3-5. It will connect to the most important paths in the Bords de Seine sector and, beyond that, to the Nanterre and La Défense areas. This link will reconcile the development of nature in the city, inter-neighborhood connections, and the discovery of a previously little-known area. Direct access to the site from the east will be provided by a footbridge that will span the RER A tracks towards the Grande Arche, continuing the historic axis. This crossing of the RER tracks will complete the neighborhood's soft connections while redesigning them and is expected to be operational by 2027.
• Defining new uses: The future programming of Terrasses 3-5, the start of Delta Vert, will rely on the “Le Pré” association to consolidate the site's agricultural and cultural vocation and its long-term management methods. This association plans to run educational workshops for architecture students and schoolchildren in Nanterre, who will be asked to reflect on this site as part of the project. Experimental research into soil decontamination will also need to be relaunched.

With the recent removal of highway ramps, the momentum generated at the Échangeur site offers significant opportunities for an iconic project that is both inhabited and oriented toward the city and nature.

From the Chemin de l’Île departmental park to Avenue de la République, the Échangeur site covers approximately 12 hectares. It is located at the junction of almost entirely redeveloped areas (Hoche district, Cœur de quartier, Terrasses 7-17) and more disparate entities (ZAC des Papeteries, Anatole France sector, Terrasses 3-5) awaiting interconnection. It is occupied:

• to the west, by the entrance and exit ramps of the A14-A86 interchange,
• to the north, by the RER A viaduct,
• to the south, by the Chemin de l'Île departmental park, which runs alongside the A14.

Between 2018 and 2021, the State and Paris La Défense carried out the burial of the B5 ramp and the redevelopment of Avenue de la Commune de Paris.

Following the example of the République-Université and Terrasses 3-5 sectors, opening up the site involves creating new connections and opening it up to the city. Landscaping and pedestrian links will thus be created on the A86 motorway cover and/or the gaps in the RER A viaduct.

This opening will provide new access to the Chemin de l'Ile departmental park, through the creation of an extension currently under consideration with the Hauts-de-Seine Department, thereby enhancing the site's wildlife and rich biodiversity. The green corridor from the Terrasses will finally be completed with this last link connecting it to the banks of the Seine.