jungletoad: Here are a few shots I took from the absolutely breathtaking Outerra: Anteworld.
This is the alpha build of a new graphics engine that uses procedural generation techniques to create an entire planet with different biomes for deserts, grasslands, snowy fields, etc. The results are stunning and the world is immense. This might very well be the future of open world games. This is the latest version which has added in animated blades of grass that move with the rolling wind, and water that rolls into the coastline in waves.
Gamers are only interested if they can f--k that world up, GTA-style. ;-)
Seriously, though, that does look pretty awesome.