Lots of ways to create a city, but it depends on what you want to do...

1. realistic city, close-up - buy some of the buildings (e.g those by Alain Garcia) at C3D and lay out the city with them;

2. sci-fi city - buy the 'Dystopia' blocks also from C3D;

3. model your own buildings as required to make a city of any kind, I would think that you can do this using Vue primitives to a great extent, and Vue has some good 'building' textures;

4. for vast cityscapes you can use terrains with greyscale maps to generate the building shapes, see this image I did a while back: http://www.renderosity.com/mod/gallery/index.php?image_id=1165820

There are probably many other ways!

Steve