Cube in Cloud: Recycled Iron Frames Turn a Disused Paris Railway into a Living Public Spine

Most cities treat a dead railway as a problem to be paved over. Cube in Cloud, also titled la fierte de_KMU, starts from the opposite assumption: the abandoned rail line is already a piece of infrastructure, already a continuous public corridor waiting for occupants. Instead of erasing the tracks, the project recycles them, threading a lightweight modular platform through the void and turning a strip of industrial decline into a sequence of rooms for culture, trade and rest.

The proposal comes from Chanyoung Kim, 김신홍, 혜진 이 and 동헌 최, who set their scheme on closed railway sections in Paris. These remnants no longer carry trains, but they still cut linear gaps through the dense urban fabric, splitting neighbourhoods and creating the kind of unwatched space that feels unsafe after dark. The team answers with a kit of standardized units built from recycled materials, a coupling system for quick assembly and disassembly, and a programme broad enough to keep the corridor busy from morning into night.

A Sunken Rail Corridor Reframed as Urban Room

The opening rendering sets the tone: a sunken green strip, flanked by thin steel frames, white platforms and railings, sitting beneath a canopy of mature trees. Nothing here tries to compete with the setting. The frames read almost as drawing lines, marking edges and levels while leaving the trench, the trees and the sky to do most of the spatial work. It is a confident decision to let the existing cut in the city remain legible.

The site plan explains why that restraint matters. The building is a narrow green sliver wedged between active tracks, wide roads and surrounding blocks, a leftover in every sense. By reading this sliver as an elevated landscape rather than a residual gap, the designers convert a barrier into a connector. The corridor becomes a public spine that stitches together the edges it once divided.

Stacked Platforms Built from a Coupling Kit

The monochrome view along the retaining wall reveals the system at work: platforms stacked over one another, stairs linking the levels, slim canopies hovering above, bare winter trees behind. Every element appears to come from the same small vocabulary of standardized units. The coupling system lets these units join in endless configurations and come apart again, which makes the architecture scalable and responsive rather than fixed to a single plan.

This is where the project earns its sustainability claim. The structure uses recycled iron components and materials already circulating within existing recycling systems, and the team designs around recyclable restraint forms so that the frames can return to that loop at the end of their use. A metal recycling circulation diagram in the proposal maps this closed cycle. The building is treated less as a permanent object and more as a temporary arrangement of material passing through the city.

Grass Strips and Stepped Seating Keep the Void Occupied

At ground level, the corridor softens. A lawn strip runs beside a concrete wall and stepped seating, and figures lounge on the grass beneath light frames and canopies. The central grass strips between modules act as micro-habitats, bringing vegetation back into a corridor that industry stripped bare and giving the city a continuous green line where it had a fenced void.

Programme does the rest. The modules host exhibitions, workshops, performances, flea markets, rest areas and cafés, arranged as a sequence of zones that encourages people to keep walking and stop often. The designers frame this mix explicitly as a CPTED strategy, Crime Prevention Through Environmental Design: more visibility, more types of users and continuous activity make the space safer simply by keeping it watched and used. It is a pragmatic argument, and a convincing one for a site whose main problem has been emptiness.

Light Lines That Hold the Corridor After Dark

The night rendering shows the frames at their most expressive. Glowing light lines trace the structure and railings above a water channel, while a lone figure with an umbrella crosses in the rain. Integrated neon lighting turns the modular skeleton into a luminous landmark, giving the corridor an identity that daytime greenery alone could not supply.

The lighting also completes the safety logic. A corridor that disappears at night undoes whatever activity it gathers by day; one that glows invites passage and keeps sightlines open. A controlled maximum height of 6,900mm keeps the whole assembly visually permeable, so the platforms float above the railway like the cloud in the title instead of walling it off.

Why This Project Matters

Cube in Cloud addresses a condition that repeats across global cities: rail infrastructure built for growth and then left to fragment the neighbourhoods around it. Its strongest move is a refusal to demolish. By recycling both the corridor and the materials placed on it, the project shows how adaptive reuse, modular construction and environmental responsibility can operate as a single strategy rather than three separate ambitions.

What makes the proposal persuasive is its lightness. Thin frames, a reversible coupling kit, grass strips and light lines ask very little of the site while changing how it is used and perceived. The open question for a scheme like this is governance: who decides how the modules are rearranged over time? Even so, as a prototype for public infrastructure that can grow, shrink and eventually return its iron to the recycling loop, it offers a clear and replicable model for urban regeneration.

View the Full Project

About the Designers

Designers: Chanyoung Kim, 김신홍, 혜진 이, 동헌 최

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Project credits: la fierte de_KMU by Chanyoung Kim, 김신홍, 혜진 이, 동헌 최.