Thunder Rift
Thunder Rift is a setting created in the 90's for the "basic" Dungeons & Dragons product line. The setting, an alternative to the Known World/Mystara (the standard D&D setting), was conceived as a starting point for beginning game groups and to be gradually expanded by the DM. The Thunder Rift worked as a self-contained setting, but could be inserted in any existing game world as well.
Read more about this topic: Dungeons & Dragons Campaign Settings