Large Biome worlds are generated as Default worlds, but 16x bigger. A Default and Large Biome world sharing the same seed will be the same overall geographically, but the Large Biomes world will be approximately 16 times bigger, with the x and z axis multiplied by 4.
In order to create a world with large biomes in SMP, the level-type flag in server.properties must be "LARGEBIOMES", instead of "DEFAULT".
|1.3.1||12w19a||Large Biomes introduced.|
Example of a massive Plains/Extreme Hills Biome on a map.