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!

For this image, I downloaded the demo version of Google Sketchup Pro, then downloaded a couple dozen building models with photographic textures and exported them as 3DS models. Then I put together an ecosystem and voila!

Thanks guys but do any of you know how i could accurately model New York are there any free DEM maps of around the coast and as far in as Brooklyn bridge

Some cases layering terrains (symetrical and non) works, using grayscale displacement mapping. (This is just using Vue 4 D'Esprit)

Then add a few modeled buildings too, the above images still needs a bit of tweaking, moving the terrain layers up and down..