Most "buildings" in The Line are in the 500m-high walls, with public space and facilities like this sports stadium between them. Note the mirror glass on the outside of the wall.
Finally, someone has invented the future. And it's none other than Mohammed bin Salman, Crown Prince of Saudi Arabia! In his new city, everyone will live very closely together, with all their daily needs – work, school, community activities, recreation – within a five-minute walk.
Every home will have greatviews. Energy and water will be 100 per cent renewable, temperatures will be fully controlled and autonomous machines will do everything from shopping to cleaning the apartments. There could be an artificial moon.
It's called The Line: a "revolution in civilisation" designed to "protect and enhance nature" and by 2030 this extraordinary city could largely be built. The design is by Morphosis Architects, a US-based firm founded by Pritzker Prize winner Thom Mayne. The budget is close to a trillion New Zealand dollars.
The Line will consist of two parallel walls, 500m high (that's taller than the Empire State Building), with homes, commercial buildings, vertical farms, schools and other services fitted into them. The exteriors will be mirror glass, with the stark beauty of the desert beyond. The public spaces between the walls will be parklands and waterways, designed for "an optimal balance of sunlight, shade and natural ventilation". The city will stretch for 170km, with a high-speed railway making the journey from one end to the other in 20 minutes.
Those walls will become the world's largest structures, and yet the whole thing will be just 200m wide: the width of two rugby fields. Nine million people will live there.
And none of them will own a car. There won't even be any roads.
That's right: Saudi Arabia, the world's second-largest oil producer, is building an enormous car-free city, protected from all the adverse effects of climate change, using the billions it makes from reinforcing car dependency in the rest of the world.
"You see desert," they say, "we see opportunity." The place will be "a living laboratory, home to the brightest minds, dedicated to the sanctity of all life on Earth".
"All life", presumably, doesn't include the people Saudi Arabia routinely imprisons, tortures and often executes for such "crimes" as being raped, "behaving" in some LGBTQI+ way, criticising Mohammed or being a woman who leaves the house without permission. Or the untold number of workers, most of them migrants and treated little better than slaves, who will build The Line.
The value to MBS is clear enough: he wants to be known as a visionary world leader and not the guy who ordered the murder and dismemberment of journalist Jamal Khashoggi.
For the rest of us, extraordinary architecture is probably not the future but does pose a challenge. The Line asks us what we value in cities and how we might reconceive them in a zero-emissions, equitable way. We're not going to build our own Line in the sand, so what will we do instead?
It's also a warning. The Line affirms that the mega-rich will be just fine, whatever global warming does to the planet. They will build themselves fabulous pleasure cities, insulated from the world as it turns to desert.
And they will carry on mega-polluting, while their lackeys in politics and the fossil-fuel industries keep assuring the rest of us we really don't need to worry. We're going to see more projects like this.