> In a fully developed nano technological society, matter will be almost
> synonymous with "thought.'" What you dream up, you can make.
I think this means that it will not be possible to generalise about nano cities; some might be built underground, other soar into the skies. The material constraints are still there, but so relaxed compared to current ones that the cities can indeed look like anything.
However, all the wonderful ideas posted here assume a modernistic planned city, with somebody who says "Hey! Let's build Transburg underground!" or "What if we made New Muse City *mobile*?" and then a big project to implement it. A more realistic situation would be the gradual retrofitting of current cities and the emergence of new cities, likely with even less central planning than today (given that the assumed level of nanotech is so strong there is no need for much centralisation; in a feed scenario a la the Diamond Age other forms of cities make sense).
So what I would expect is that many cities would have old-style cores, containing medieval to modern buildings carefully renovated by the antiquarians. They might simply be tourist traps, or actually used. Around them (and "around", given the transportation possibilities of nanotech, could be very far) "modern" buildings would appear. The first ones would simply be something similar to today's architecture, improved by new materials (I expect that somebody will build super-skyscrapers just to show off), while as nano goes on and architects learn to use the material they become more diverse.
So my vision of the nanotech city would be a garden sprawl, with dotted superskyscrapers, underground buildings, a very powerful nano-based transportation infrastructure of some kind, and an old-style core.
Then again, the city *I* want to live in is the waterfall city on the artificial continent Forrest Bishop and I discussed two years ago on this list (maybe we ought to write it up and do some engineering calculations on it). I want to live in a tower high up in a city built in and around a series of great waterfalls. At the top there is a freshwater lake that falls down in cascades through this very 3D city, at the bottom the water vanishes into a dense jungle. The building-towers are connected by bridges and movement is mainly by elevators. Terraces with gardens dot the city, covering most buildings with greenery.
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