Scene City (previously Suicidator) is a city generator, it lets you build entire 3D cities very easily, big or small, with a high visual quality. It is meant to be used along with Blender.
Start by setting your city options in the generator, an easy to use standalone 3D application for Windows, Mac and linux
Walk in your city with a first person camera, or fly over it, all in realtime
Export your city as a .blend file that can be directly opened in Blender, the powerful and free 3D creation application
On export, your city is automatically opened and ready in Blender for you. Position the camera, hit F12, save the render, done!
Render your city in Blender Internal for fast renders, or in Cycles for the highest quality, choose whichever you need
Blender veterans, the cities are made so that you can use your Blender skills to customize the cities very easily, anyway you like