From Wikipedia:
The Aeropolis 2001 is a proposed project for construction of a massive 500-story high-rise building over Tokyo Bay in Japan. It is proposed to be a 2,000 metres (6,562 ft) high building. If built, the mammoth structure would be approximately five times as high as the former World Trade Center was in New York.
Envisioned by Obayashi Gumi Corporation, it is with 500 floors that would accommodate over 300,000 inhabitants. The structure is expected to be mixed-use, including restaurants, offices, flats, cinemas, schools, hospitals, and post offices. Elevators are expected to travel from top to bottom in 15 minutes. The tower is proposed to be fully sustainable and air conditioned.
http://www.emporis.com/en/il/lv/?id=138681
A scan from an old Popular Science issue