If you have iPhone (3GS or newer) or iPad, this demo of Epic technology is stunning running on the IOS platform.

iTunes Link:  Epic Citadel

source: http://toucharcade.com/2010/09/01/unreal-engine-3-tech-demo-epic-citadel-available-for-free/

(if you don’t have one of the devices, you can view the video of it below.)