X-Seed 4000 or Ocean City is the name of a visionary skyscraper design from 1980 . Designed for the home, work and leisure of a million people, it is the tallest skyscraper vision ever proposed; The 800-storey and 4,000-meter-high building was designed for an artificial island in Tokyo Bay off the Japanese coast. Individual building cells were to be hung into the open structure, which is reminiscent of a volcanic cone due to its conical shape , for which around 500 million tons of steel were estimated and which should have a diameter of around six kilometers. The development should take place with up to 200 people in elevators inside the huge steel pipes. A trip to the top would have taken 30 minutes. A dense settlement was only planned up to 2000 m altitude, above that the supply of oxygen and heat would have become too expensive. The Tasai Corporation , from which the proposal came, estimated the construction time at 30 years. It is believed that the construction costs of the X-Seed 4000 would be between € 238 billion and € 712 billion. That was roughly half of Japan's GDP in 1980.
The New York artist Tobias Bernstrup was inspired by X-Seed 4000 for an art project of the same name.