World’s tallest skyscraper would have 800 floors, reach 2.5 miles high and house 1m | World | News

The current record for the world’s tallest building is held by Dubai’s Burj Khalifa, but a concept conceived three decades ago would tower five times higher if it ever comes to fruition.

First unveiled in 1995, the design known as the X-Seed 4000 would easily become the loftiest skyscraper ever constructed. It’s projected to reach an astonishing 4km (or 13,123ft/2.5 miles) into the sky, making it nearly half the height of Mount Everest.

The Japanese construction company behind the project, Taisei Corporation, reportedly envisioned it floating on Tokyo Bay, with other Asian locations also under consideration.

This incredibly ambitious venture proposed providing homes for between 500,000 and one million residents across its 800 floors.

An estimated 3,000,000 tons of steel would have been needed for the complex undertaking, with internal air pressure regulations considered to prevent altitude-related illnesses among inhabitants.

Recently discussed on LinkedIn, the floating city, spanning 6km wide, was analysed by Reuben Petty who shed light on the dream that never materialised.

He explained: “Its form was inspired by Mount Fuji, featuring a broad, stable base gradually tapering to a majestic peak. This pyramidal shape was not purely aesthetic; it was intended to provide structural stability against the forces of the ocean and potential seismic activity, a significant concern in the Tokyo Bay area.”

The masterminds behind it envisioned it would be a self-sufficient artificial island supported by floating caissons.

Rather than simply comprising flats, the ambitious plan was for it to function as a complete city in its own right, featuring business hubs, commercial zones, leisure facilities and research establishments all housed on-site.

Speculation emerged in 2007 that Taisei planned to proceed with the ambitious scheme, but these rumours were quickly dismissed.

George Blinder, managing director of Buildings and Data, revealed at the time: “It was never meant to be built. The purpose of the plan was to earn some recognition for the firm, and it worked.”

Confirming that the skyscraper was no longer under consideration, Shohei Ogawa, a planning manager at Taisei, stated X-Seed 4000 was “on the shelf now”.

He added: “It was our dream proposal for the technological advances we thought that could happen in the future.”

Erik Howeler, an architect and author of Skyscraper: Vertical Now, told Architectural Record that constructing such a towering structure was “possible” from an engineering standpoint.

Nevertheless, from a practical perspective, he believed the estimated $1 trillion price tag would prove challenging, alongside securing approval to erect such a colossal building. He added: “Tall buildings create a downdraft at their bases, and cast long shadows.”

The project, which has sparked safety and environmental debates, was a hot topic on Reddit.

One user compared it to a video game, stating: “This literally looks like the city seen in high charity mission in Halo 2.”

Another drew parallels with a film, commenting: “That’s genuinely just the star harvester from Transformers 2.”

A third voiced concerns about practicality, saying: “Imagine the elevator not working and you live on the 657th floor.”

One person questioned the use of resources, adding: “Ah yes, let’s waste resources to build some massive building.”