:X-Seed 4000

{{short description|Proposed hypothetical arcology}}

{{Verification|date=November 2022}}

{{Infobox building

| name = X-Seed 4000

| native_name = X-Sen Shushi 7000

| native_name_lang = Japanese

| status = Proposed

| image = X-seed4000.jpg

| caption = The design of X-Seed 4000

| location = Tokyo, Japan

| coordinates =

| floor_count = 700

| cost = 900B to 1.7T

| highest_prev =

| building_type = Mixed use

| roof = {{convert|4000|m|ft|0|abbr=on}}

| developer = Taisei Corporation

}}

File:XSeed4000BurjDubaiComparison.jpg]]

The X-Seed 4000 was a concept for a megatall skyscraper.{{Cite web |last=Anissimov |first=Michael |date=Feb 16, 2006 |title=Accelerating Future » X-Seed 4000 |url=http://www.acceleratingfuture.com/michael/blog/2006/02/x-seed-4000/ |url-status=dead |archive-url=https://web.archive.org/web/20080618150549/http://www.acceleratingfuture.com/michael/blog/2006/02/x-seed-4000/ |archive-date=Jun 18, 2008 |access-date=2022-11-25 |website=acceleratingfuture.com}} Its proposed {{convert|4|km|mi|adj=mid}} height, {{convert|6|km|mi|adj=mid|-wide}} sea-base, and 800-floor capacity could accommodate 500,000-1,000,000 inhabitants. This structure would have been composed of over {{convert|3|e6t|e6ST|abbr=unit}} of steel.

It was designed for Tokyo, Japan, by the Taisei Corporation in 1995 as a futuristic environment combining ultra-modern and technological living and interaction with wildlife and nature.{{Cite web |date= |title=Digital Studio - Contemporary Theories of Architecture Brief |url=http://digitalstudio.gre.ac.uk/content/view/125/31/ |url-status=dead |archive-url=https://web.archive.org/web/20060518173240/http://digitalstudio.gre.ac.uk:80/content/view/125/31/ |archive-date=2006-05-18 |access-date=2022-11-25 |website=digitalstudio.gre.ac.uk}}{{Cite web |date=2004-05-04 |title=Taisei Construction Co. Ltd. |url=http://www.emporis.com/en/cd/cm/?id=100207 |url-status=usurped |archive-url=https://web.archive.org/web/20040504115106/http://www.emporis.com/en/cd/cm/?id=100207 |archive-date=2004-05-04 |access-date=2022-11-25 |website=Emporis}} Methods of transportation within the X-seed would most likely include Maglev trains.

Georges Binder, managing director of Buildings & Data, a firm which compiles data banks on buildings worldwide, said the X-Seed 4000 "is never meant to be built{{nbs}}[...] the purpose of the plan was to earn some recognition for the firm, and it worked."{{Cite web |last=Lubell |first=Sam |date=September 12, 2007 |title=X-Seed Inspires Tall Tales {{!}} 2007-09-12 {{!}} Architectural Record |url=https://www.architecturalrecord.com/articles/3947-x-seed-inspires-tall-tales |access-date=2022-11-25 |website=www.architecturalrecord.com |language=en}}

Unlike conventional skyscrapers, to remain habitable the X-Seed 4000 would have been forced to actively protect its occupants from considerable internal air pressure and external air pressure gradations and weather fluctuations that its massive elevation would cause. Its design called for the use of solar power to maintain internal environmental conditions. As the proposed site for the structure is located in the Pacific Ring of Fire, the most active volcano range in the world, the X-Seed 4000 would have been vulnerable to earthquakes and tsunamis.

A sea-based location and a Mount Fuji shape were some of this building's other major design features—Mount Fuji itself is {{convert|3776|m}} high, making it {{convert|224|m}} shorter than the X-Seed 4000.

The X-Seed 4000 was projected to be twice the height of the Shimizu Mega-City Pyramid at {{convert|2004|m}}.

The Shimizu Mega-City Pyramid (also planned for Tokyo, Japan) faces most of the same problems as the X-Seed. Other projects that, if built, could be in the top five human-made structures are the Ultima Tower of {{convert|3218|m}} in San Francisco, Dubai City Tower of {{convert|2400|m}} and the Bionic Tower of {{convert|1228|m}} in either Hong Kong or Shanghai.