(Segment of a drawing of Macro-Cosanti, from http://www.arcosanti.org/soleri_archives/macroco/macropan.html)
The concept of arcology (a combination of architecture and ecology) has been championed by Italian architect, designer, and artist, Paolo Soleri. The idea is to build a highly dense urban environment in an extremely compact 3D space, rather than the traditional urban sprawl we see in current cities.
The only arcology yet on Earth is still in its prototype stage in Arizona. It's called "Arcosanti" and you can find info about it on their website at http://www.arcosanti.org/ including pictures of their daily progress in building the arcology. Arcosanti is designed so that when completed, approximately 7000 people will live in a densely populated, car-free area of about 25 acres, in the middle of a 4060 acre nature preserve. You can walk anywhere in the city within a few minutes, and similarly, you can be outside of the city and in the middle of desert wilderness within a 5-10 minute walk. (There's certainly much to be said in favor of this design over our current high-traffic, congested streets and highways, and highly polluted cities with token parks to let people "get away" from the pressures of the City.)
This view is from http://www.arcosanti.org/soleri_archives/mesa/mesa.html
This view is from http://www.arcosanti.org/soleri_archives/arcolo/arcolo.html and was drawn by Junji Shirai in November, 1968.
Arcologies also play a part in the urban-planning games "SimCity? 2000" and "SimCity? 3000", where they form a part of the futuristic landscape and provide high-density living for 80,000-150,000 people.