City Engine is a modeller for urban landscapes that ESRI acquired to complement their ArcGIS software. A new version has recently been released and is available under our academic license with ESRI.The main ESRI site for City Engine has a number of examples showing the features of this software.
This software is very graphics intensive and it requires a higher end graphics card. If you do not have one of the supported cards, the installation process will warn you. You may want to stop if you see that warning. However, all that is really required is a card that supports OpenGL. (ESRI has a blog post that describes how to check to see if your card supports OpenGL.)
OpenGL is available for academic (teaching and research) purposes, but not administrative uses.
City Engine is available for Windows, Linux and Macintosh computers.