I recently came across this fantastic article that ties in nicely with my recent post about game environments. The author is Tom Betts, who is a PhD researcher and computer programmer working on procedurally generated game environments. For an example, check out this amazing video that shows gameplay for an entirely procedurally generated environment, including the music!! Awesome stuff.
In the article linked below, Tom writes about several games which are known for their stunning environments. The environments in these games were not just for exploration, they were the main character in the game story.