iClone combines 4 video production with 3D real-time animation, the software integrates with various 3D packages, including SketchUp and provides a quick and easy way to add animation to scenes.
The clip below provides an overview:
Of particular note are the city expansion packs, allowing complex cityscapes to be built quickly and easily.
City Blocks Vol. 1-Skyscrapers in Metro City:
For more information head over to http://www.reallusion.com/iclone/
Also take a look at Reallusions uploads to the Google 3D Warehouse, there are a range of useful street, park and city elements.