Saudi Arabia’s Crown Prince Mohammed bin Salman has announced plans for radical new city development in the northwest of the country, in a section of desert close to the Red Sea. The city will run entirely on renewable energy and eventually be home to around 9 million people.

Yet, the real eye-opener of this futuristic metropolis is the design of the city’s buildings themselves, or should we say, “building”, as the city will be called “The Line” and comprise a single, massive wall-like structure that will extend for 170km, while standing 200 meters wide and 500 meters tall. If everything goes to plan, this single-building city will easily break the record for the world’s largest building.

The massive development is part of Crown Prince Mohammed bin Salman’s NEOM project, which plans to turn a remote area of the country into a high-tech semi-autonomous state. The plan hopes to attract foreign investment and eventually usher Saudi Arabia into a post-oil economy.

Technical details about the project are scarce. However, there’s no denying the plans look impressive: A recently released video shows a striking mirrored glass facade, three-dimensional living, plenty of green spaces, and multi-level walkways, with high-speed travel that connects each end of the structure in just 20 minutes.

Despite inspirational taglines such as “a civilizational revolution that puts humans first”, the scheme has attracted criticism, with some architects finding the design a little too dystopian for their tastes. Crown Prince Mohammed bin Salman has said that The Line will embody “Zero Gravity Urbanism” and has issued a statement about his ambitious project:

“The designs revealed today for the city’s vertically layered communities will challenge the traditional flat, horizontal cities and create a model for nature preservation and enhanced human livability.”

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So when can we hope to see the foundations laid on this futuristic project? So far, the NEOM project has received $500 billion in backing from the Saudi Arabia government and the Saudi Arabian Public Investment Fund. Plans were initially scheduled for 2025 but have since been postponed by another 5 years, though officials insist the project remains on track.