NUAGE: A Parametric Cloud Suspended Over the Disused Rails of Paris' Petite Ceinture

Paris has spent a century and a half perfecting its own regularity. Haussmann's boulevards, the continuous cornice lines and the steady rhythm of its blocks have produced a city so legible that any break in the pattern reads as a wound. NUAGE goes looking for exactly that kind of break and decides not to heal it. Instead, it takes the grid that defines Paris, bends it until it behaves like a cloud, and drops it into one of the city's longest forgotten voids.

Designed by Aylin Toprak and Elif Gencer, the project targets La Petite Ceinture, the disused railway loop that runs through the city's dense and highly ordered fabric as a linear strip detached from everything around it. Rather than filling the cut with a conventional building or a tidy park, the designers treat the corridor as a testing ground, positioning their proposal between heritage preservation and experimental parametric design.

A Repetitive Grid That Learns to Drift

The opening view lays out the project's central argument in a single frame. A long steel trellis runs along the corridor with the discipline of a Parisian street wall, yet its profile swells and softens as it moves, and hanging vines blur its edges further. The designers begin with a strict repetitive grid as a stand-in for the formal rigidity of the city, then deform it parametrically at chosen points along the site. The result is a sequence of spatial events rather than one uniform structure, each deformation breaking the predictable urban rhythm the visitor has just left behind on the street above.

The name follows directly from this move: nuage is French for cloud, and the deformed surfaces are meant to read as a cloud caught inside the grid. What makes the idea persuasive is that the cloud never fully escapes its origins. The structure stays visibly gridded, so the disruption remains legible as a disruption, a measured critique of Parisian order rather than an outright rejection of it.

Suspended Above the Tracks, Anchored at the Edges

Beneath the canopy, the steel framing and dense foliage form a sheltered walkway, and the rainy scene in the render makes a quiet case for that cover. The more important decision, though, is structural. The system is elevated and anchored along the edges of the cut, keeping its physical contact with the historic railway to a minimum. The tracks remain intact beneath a lightweight frame that could, in principle, be removed without erasing what came before.

This is a sensible answer to a site that carries heritage weight. Too many reuse proposals for abandoned rail lines pave over the very infrastructure that gives them meaning. NUAGE treats the railway as something to hover above, letting the new public realm and the old infrastructure occupy the same corridor without competing for it.

Seven Metres of Depth Turned Into a Programme Stack

Most activity on the Petite Ceinture sits roughly 7 metres below street level, a condition that usually makes such sites feel cut off. The designers amplify that depth instead of flattening it. Multiple levels of occupation link street and subterranean spaces through a continuous system, so different activities can stack and coexist without interfering with one another. The two interior views show what that looks like in use: musicians playing in an aisle lined with vine curtains, and an audience seated on a lawn inside the lattice hall, facing a screen beside a wall of flowering vines.

Neither scene depicts a programme the building was designed around, and that is deliberate. NUAGE avoids prescribing uses, positioning the parametric grid as a framework that residents and visitors can take over as they see fit. The concert and the screening read as two possible occupations among many, which suits the project's stated aim of building a shared platform for inclusivity and social cohesion across the city's cultural and social divisions.

Recycled Steel Below, Printed Plastic Within

The final image moves onto a mesh-floored walkway threaded through the frame, with planter boxes of flowers at its edge and an elderly couple strolling alongside a pointing visitor. The scene shows the project at the scale of the body, and it brings the material logic into view. The primary structure is recycled steel, chosen for durability, recyclability and structural efficiency. Secondary components are made from recycled plastic through additive manufacturing, designed as modular, prefabricated pieces for efficient assembly on site.

Pairing a recycled structural skeleton with printed infill gives the parametric geometry a believable route to construction. Every deformed module can be fabricated individually without the waste of custom formwork, and a prefabricated kit of parts fits the light-touch approach the structure already takes toward the railway below.

Why This Project Matters

Parametric design is often criticised for producing form for its own sake, and urban reuse projects are often criticised for timidity. NUAGE manages to avoid both traps. Its geometry carries a clear argument about Paris, a rigid order loosened at selected moments, and its spatial strategy draws on the most awkward feature of the site, the 7 metre drop, to create a layered public realm rather than treating that depth as a problem to engineer away.

Just as significant is what the proposal refuses to do. It does not erase the railway, it does not fix a programme, and it does not pretend the void is anything other than a void. Toprak and Gencer offer a framework light enough to sit over heritage and open enough to be claimed by whoever arrives. For a city defined by its consistency, that combination of restraint and disruption makes a compelling case for how Paris might occupy its leftover spaces.

View the Full Project

About the Designers

Designers: Aylin Toprak, Elif Gencer

Enter a Design Competition on uni.xyz

uni.xyz runs architecture and design competitions year-round that reward proposals with spatial conviction and real site intelligence.

Project credits: NUAGE by Aylin Toprak, Elif Gencer.