Are you looking for the bright and shiny futuristic cities or the dark and dystopian ones? The traditional megalopolis, an elite floating (or even orbital) habitat, an off-world city or something like a middle-class suburb? The problem with "sci-fi" is that it means something very different to different groups of people, I think.
I have this suspicion that city layout won's be too much different from the ones that we have now. Perhaps take an existing city and replace a random blob with a megablock or three (chrome spires with bubbles and tubes for the happy future, dirty gray cubes for the unhappy one). http://joannapary.files.wordpress.co...1/dystopia.jpg nicely sums up the unhappy one, I think.