The first hive city I mean Arcology

The X-Seed 4000 is the tallest building ever fully envisioned, meaning that the designs for construction have been completed. However, due to excessive projected costs, the structure has not been constructed.

Its proposed 4 kilometer (13,123 foot) height, 6 kilometre wide sea-base, and 800 floor capacity could accommodate five hundred thousand to one million inhabitants.

It was designed for Tokyo, Japan by the Taisei Corporation in 1995[1] as a futuristic environment combining ultra-modern living and interaction with nature.[2]

Unlike conventional skyscrapers, the X-Seed 4000 would be required to actively protect its occupants from considerable air pressure gradations and weather fluctuations along its massive elevation. Its design calls for the use of solar power to maintain internal environmental conditions.

A sea-based location and a Mount Fuji shape are some of this building's other major design features — the real Mount Fuji is land-based and is 3.8 kilometers in height, nearly 213 m (700 feet) shorter than X-Seed 4000.

Some estimate that the cost to construct the X-Seed 4000 structure may be somewhere between US$300-900 billion, in current dollars.


I doubt this will work just from a stable geography point of view of Japan.