1. DIB-200: An 800m, 200-story building. By the standards of the era's plans, this was actually considered 'modest.' It featured a modular design with 12 cylindrical modules and was meant to be a mixed-use complex for offices, hotels, and housing, with a capacity of 50,000 people.

AI Translated Image

2. Millennium Tower: An 800m, 150-story skyscraper planned for an artificial island. It aimed for multi-purpose use including office, residential, commercial, and cultural spaces. 'Sky Centers' with hotels, shops, and sports facilities were to be placed every 30 floors. It featured 160-passenger linear elevators, a capacity of 20,000 people, and a 10-year construction plan with a budget of 1.6 trillion yen.

3. Sky City 1000: Just like the name implies, a 1000m tall skyscraper. The concept involved a massive green space in the center, surrounded by residential, educational, office, and commercial facilities. The hexagonal floor design was meant to minimize wind resistance and fire hazards. Capacity: 100,000 people.

4. TRY-2004: A pyramid-shaped megastructure 2004m tall capable of housing 1 million people. The goal was completion by 2004 with a 7-year construction period. It featured a truss-structure 'skeleton' containing dozens of smaller buildings inside for housing and offices. Maintenance was to be handled by robot systems, with transportation via inclined elevators.

AI Translated Image

AI Translated Image

5. X-SEED 4000: A literal mountain of a building at 4000m high and 6000m wide. It would have been bigger than Mt. Fuji (3,776m). With 800 floors, it featured solar power generation and a capacity for over 1 million people. Construction costs were estimated at over 150 trillion yen with a 30-year timeframe; in today's money, that's roughly $1.5 trillion.

AI Translated Image

6. Tokyo Babel Tower: Proposed in 1992 by Professor Toshio Ojima of Waseda University, this is on a whole different level. 10,000m tall with a ground area of 110km² and a population of 30 million. It even included a space development center at the summit. Underground power plants, housing/commercial up to 1000m, hotels/offices up to 3500m, education/leisure up to 6000m, industrial/research up to 9000m, and solar/space facilities at the top. Construction was estimated at 150 years with a cost of 3,000 trillion yen (about 3.4 quadrillion KRW). This is equal to 30 years of Japan's national budget or 6x their GDP. The reason for these megastructures? Land prices during the bubble were so insane that they tried to fit as much as possible on the smallest footprint possible.