In a vast desert in Saudi Arabia, a colossal project advances with relentless machinery, cranes, and teams shaping the sands for a plan that seeks to redefine urban living. The Line is a linear city described earlier in media reports. It stretches 170 kilometers in length, is 200 meters wide, and rises 500 meters high. The regime frames the project as a model of sustainability, a bold leap toward the future.
Yet the big question persists: can such a megastructure truly be sustainable when weighed against its environmental footprint? Architect Luis Lope de Toledo, known for sharing insights on social channels devoted to these topics, has produced a full analysis of environmental impacts and livability. His verdict is clear in his video: a utopian and impractical dream, difficult to classify as sustainable.
One focal point is the building’s skin, a wall planned to be covered with reflective mirrors. Critics ask what happens to local birds when this vast surface becomes virtually invisible to wildlife yet highly reflective to the air and light. The concern is not just migration disruption but potential harm as birds collide with the mirrors.
Still, questions about sustainability go deeper. Crown prince Mohamed bin Salman has claimed that the city will reach a zero carbon footprint once operational. The issue, according to the architect, is that the enormous carbon cost incurred during construction may outweigh any future environmental gains.
CO2 emissions as much as the whole of London in four years
In fact, Lope de Toledo echoes Philip Oldfield, director of the School for the Environment in Sydney, who notes that a 500-meter-high building cannot be constructed with low-carbon materials alone. It requires enormous quantities of steel, glass, and concrete. Oldfield estimates the embedding of CO2 in the Line’s construction could exceed 1.8 billion tonnes, roughly equivalent to the UK’s emissions over four years.
One key claim about sustainability is the absence of cars inside. The project touts that everything is within a five-minute walk, achieved through a single 170-kilometer rail spine. The promise is a connected, walkable city where daily needs are close at hand.
But achieving this entails a high-speed rail vision. The claim is that travel along the length would take about 20 minutes, yet calculations from Lope de Toledo suggest the train would need to exceed 550 kilometers per hour and operate without intermediate stops. The world’s fastest rail system tops around 460 kilometers per hour, making this a demanding technological goal that would demand breakthroughs beyond current capabilities.
Beyond speed, the design raises questions about ventilation and climate control. A city squeezed between two walls, towering and narrow, presents uncertainties about air flow and cooling. The idea of a porous skin instead of a mirror facade has been proposed to allow air movement, a practical consideration that seems to have been overlooked in the initial plan.
All of these factors point to the ongoing need for advanced cooling and ventilation technologies, which in turn tests the project’s sustainability claims.
Water demand also emerges as a critical issue. Large quantities would be required to support residents and irrigate the imagined greenery in visualizations. The developers propose seawater desalination powered by solar energy, but experts raise doubts about whether renewable energy alone can sustain a facility of this magnitude.
At present, work is underway with heavy equipment marking the ground for the initial phase. The Line’s form is not yet fully visible, but thousands of supports are being driven into the landscape, with ambitious daily installation rates reported by local outlets.
Linear city, the toughest design model
Criticism continues to mount from independent researchers. A paper published in NPJ Urban Sustainability questions the linear concept as a city design, arguing that circular layouts have historically proven more efficient and resilient. The authors, Rafael Prieto-Curiel and Dániel Kondor from the Center for Complexity Science in Vienna, contend that starting from scratch to rethink a city must consider thousands of years of urban evolution toward circular forms.
Mobility emerges as the central challenge. The Line’s layout makes pedestrian connectivity within the city unrealistic as a sustainable baseline. On average, residents could be separated by significant distances if one assumes one kilometer as a walking unit. Estimates suggest only a small portion of the population would be within a feasible walking range of each other.
To address this, the project proposes a network of high-speed rail stations. Yet the report’s authors caution that creating a dense station matrix would slow travel, reducing top speeds and undermining the intended efficiency. Their calculations indicate a typical journey would span about an hour, with many residents facing longer trips than expected.
These critiques underscore the broader question: can a single, linear corridor truly deliver a practical, sustainable city? The debate continues as experts weigh the engineering ambitions against ecological and social costs.