Imagine you are playing a Zelda or Elder Scrolls game next generation and there are no artificial borders for a hundred miles in either direction. Through traditional methods of building worlds; this would not be possible for two reasons-- one, it's just too much work; and two, you couldn't put it on a disk. The way to create a large landmass is to first create the predesigned area in which the main quest takes place; and then implement procedural landscape generators with certain presets (such as range of elevation; densities of forests, grasslands, and bodies of water; types of plants and rock to be generated; etc) which create the land as the player ventures beyond the starting landscape and use the player's hard drive/flash card to save the data from the landscape as they generate it so it can be reloaded when the player moves through it again. http://youtu.be/xpGLIN4lfsE The player would be limited only by the amount of storage they have for saves. The developer could also put in rules that after the player travels X number of miles beyond the borders of the original valley; the game would load secret predesigned areas, castles, and characters. If the landscape can be randomly generated beyond the main quest; then it's possible to create settings to populate the generated terrain with friendly AI, wildlife, and monsters. The use of randomly generated landscapes with high level next generation graphics can not only be used for adventure games; the mechanic could be used to create a driving experience in which the player drives in one direction down a road for five hours. The driving experience may be even easier to randomly generate as you can already see random generation of cars and cops in GTA.