The Line © Shutterstock



Why Saudi Arabia’s “The Line” is not a revolution in urban living

What some consider an ideal ecological city, others call a promotional gimmick.

Researchers from the Complexity Science Hub now show why The Line should not be a showcase for future cities. 

In October, the excavation work for the superlative construction project began. “It’s the embodiment of the dream to start from scratch and completely rethink a city,” says  Rafael Prieto-Curiel, who researches cities at the Complexity Science Hub.

The Line is planned to be a city built from nothing in the desert. It is to consist of two gigantic, unbroken rows of skyscrapers, with living space in between. 170 kilometers long. 200 meters wide. 500 meters high, higher than any building in Europe, Africa, and Latin America. String straight ahead from the Red Sea to the east.


The Line © Complexity Science Hub, Rafael Prieto-Curiel


Nine million people are expected to live in it. More than in any other city in Saudi Arabia. This translates into a population density of 265,000 people per square kilometer – ten times denser than Manhattan and four times denser than the inner districts of Manila, currently estimated to be the densest urban neighborhoods on Earth. “How you can attract that many people in a medium-sized country at all is yet to be observed,” Prieto-Curiel points out.


Further questions arise in terms of mobility. “A line is the least efficient possible shape of a city,” says Prieto-Curiel. “There’s a reason why humanity has 50,000 cities, and all of them are somehow round,” he emphasizes. If we randomly pick two people in The Line, they are, on average 57 kilometers apart. In Johannesburg, which is 50 times larger in area, two random people are only 33 kilometers apart.

Assuming a walking distance of one kilometer, only 1.2% of the population is within walking distance from each other. This hinders active mobility, so people will depend on public transport. 

© Complexity Science Hub, Rafael Prieto-Curiel
a| Location of The Line in Saudi Arabia. b | Expected commuting time (vertical) depending on the number of stations (horizontal). c | Largest cities in Saudi Arabia, including the planned population of The Line.

The backbone of public transportation is planned to be a high-speed rail system. “For everyone to be within walking distance of a station, there must be at least 86 stations,” explains CSH researcher Dániel Kondor. As a result, trains spend considerable time in stations. Plus, they will not be able to reach high travel speeds between any two stations.

According to the researchers, a trip, therefore, is expected to take 60 minutes on average, and at least 47% of the population would have an even longer commute. Even with additional express lines, gains are limited due to the additional transfers necessary. As a result people would still be traveling longer than in other major cities, such as Seoul, where 25 million people commute for less than 50 minutes.


Research shows that people want to spend a limited amount of time commuting. Efficient transportation, therefore, plays a key role in the success of cities. But can these trips through the city be avoided because high density allows everything (jobs, shopping, amenities, etc.) to be available locally?

“Cities are more than a collection of semi-isolated 15-minute neighborhoods located next to each other. What sets a city apart from smaller settlements is not just its size. Rather, it’s their additional opportunities outside the immediate neighborhood – like concerts or an expanded job search – that set them apart. For this reason, we need to consider citywide transportation,” explains Kondor.


If you take The Line and make it The Circle with a radius of 3.3 kilometers, the distance between any two people would be only 2.9 kilometers. 24% of the population would be within walking distance of each other. Most mobility could be active (walking, cycling, or similar), making a high-speed rail system unnecessary. Alternatively, The Circle could allow good connectivity even with lower densities, avoiding the need for supertall buildings.


  • Two random people in The Line will be 57 km apart, almost twice as far as in Johannesburg, for example.

  • The linear shape makes the transport system vulnerable. Breakdowns could paralyze entire parts of the city.

  • Any given trip will take, on average, at least 60 min.

  • 47% of the population will have a commute longer than 60 min.

  • Only 1.2% of the population will be within walking distance from each other.

  • How to attract 9 million people in a medium-sized country with a population of 36.7 million is yet to be seen.

  • While all of the energy in The Line is to come from renewable sources, the construction phase and the enormous consumption of resources are not considered here. 


Measuring 6,000 African cities: double the population means triple the energy costs 


“This project gets people discussing urban forms, and that’s immensely important because cities, especially in Africa, are growing,” says Prieto-Curiel. Historically, cities often grew in organic ways, while planned cities often did not live up to expectations. Thus, there is a need for more public engagement about urban design on a human scale. 

Additionally, sustainability is emphasized in many aspects of the project. For example, there will be no cars for distances that are no more than a five-minute walk. This not only saves a lot of space in terms of infrastructure and parking but also reduces the number of cars. Moreover, all energy will be produced with zero carbon emissions. What is not taken into account here, however, is the construction of the skyscrapers, which requires a lot of material and energy.

“Overall, it stands to reason that other considerations may have played a role in choosing this unique form, such as branding or creating engaging social media videos. However, it is important to understand the consequences, especially if The Line is treated as a showcase for modern building and urban planning technologies”, emphasizes Prieto-Curiel.


About the study

The study “Arguments for building The Circle and not The Line in Saudi Arabia,” by Rafael Prieto-Curiel and Dániel Kondor, was published in npj Urban Sustainability.


R. Prieto-Curiel, D. Kondor
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