In 2004, Japanese engineers proposed a mile-high pyramid over Tokyo Bay, 14 times taller than the Great Pyramid, meant to house a million people, a mega-city we still cannot build

Imagine riding an elevator inside your own apartment building, going straight up through a pyramid so tall it disappears into the clouds. It’s not a movie scene. It is a real design by Shimizu Corporation, a long-established Tokyo-based construction company. According to The Guardian's report on Tokyo's unbuilt megaprojects, Shimizu unveiled its “Mega-City Pyramid” concept in 2004, and the drawings are still circulating today, more than two decades later. It was never built, and there is a specific scientific reason for this.

All of this began with a movie scene
The idea did not come from a boardroom. According to company lore, in 1982, a Shimizu employee watched the premiere of "Blade Runner," which features two giant pyramid-shaped towers looming over a futuristic Los Angeles. The idea reportedly developed over a decade, and by October 1992, Shimizu representatives were filing international patents for a pyramid city of their own.

The numbers are almost hard to believe
According to The Guardian's report on Tokyo's unbuilt megaprojects, Shimizu’s plan calls for a structure roughly 2,000 meters tall over Tokyo Bay, designed to house up to a million people, close to the population of San Jose, California The exact height is 2,004 meters (6,575 feet) according to Shimizu’s own technical specifications, about two and a half times taller than today’s tallest building, the Burj Khalifa in Dubai.

The pyramid would be built from five stacked frames, each roughly the size of the original Great Pyramid of Giza, which stood about 146.5 meters tall when completed. Stack five of those on top of each other, and you have a building nearly 14 times taller than the ancient monument and the largest man-made structure in history, if it were ever finished. And even then, it would only accommodate a small fraction of the approximately 33 million people who live across greater Tokyo, The Guardian reports.

The structure was not meant to be a conventional office tower. More than two dozen 30-story skyscrapers would hang from the pyramid’s frame by cables and connect through moving walkways, tilted elevators, and self-driving transit pods, reducing the need for cars. The structure would be supported by 36 engineered concrete piers, and The Guardian reported that robotic systems were planned to handle much of the construction and maintenance because so much of it would be out of easy human reach.

Why did Tokyo even need this in the first place
It wasn’t simply architects showing off. The project was also meant to address Tokyo's space constraints. Tokyo has spent decades running short of space. The United Nations Population Division’s World Urbanization Prospects showed the Greater Tokyo urban area as the third largest in the world in 2025, with some 33.4 million people crammed onto a coastline with little open land left. A pyramid over the bay, rather than more towers competing for scarce land, was Shimizu’s answer to Tokyo’s housing squeeze.

The material science that still says no
This is what keeps this pyramid on paper. The structure is simply too heavy to be built with conventional steel and concrete. Shimizu’s plan relies on future materials made from carbon nanotubes and graphene, both of which are supposed to be very strong and light. The trick is that “meant to be” is doing a lot of heavy lifting here. According to a 2016 study published in the journal Science Advances, the real-world strength of carbon nanotubes still falls well short of their theoretical potential, measuring 11 to 120 gigapascals in lab tests against a theoretical ceiling near 200 gigapascals, mainly because tiny defects make the material fracture earlier than expected. Simply put, no one knows how to produce these materials at the size and strength required for a mile-high pyramid.

The design also included an open lattice of megatrusses meant to flex under earthquakes, high winds, and tsunamis, with the trusses covered in solar film and supplemented by algae-based power generation. It’s a really clever piece of engineering. It just hasn't been built yet.

Will it ever happen
Shimizu said construction could begin as early as 2030, with completion around 2110, making it an 80-year build. Given where nanotube research stands today, that timeline looks more like a wish than a reality. But the pyramid was not really about breaking ground on the schedule. It was an open thought experiment, a question of how far you can push a city before it needs a whole new shape. That 2004 sketch is probably still sitting in a drawer in a Tokyo office somewhere, waiting for the science to catch up to the imagination.