Old World

Old Worlds is the Exclusive World Type. It was added in very first version of MCPE. Terrain in Old Worlds is limited to 256x256 area, that have Invisible Bedrock Barrier around it. Biomes from Infinite Worlds still exists here, but due to small area, they are 2x smaller, and not all Biomes exists here.

Before 0.9.0
Old Worlds is only one available World Type, and it don't have all Biomes, Generated Structures and Foliage Color.

Trivia

 * If you fly above Clouds, and go into Third Person Mode, you will be appear as Invisible, and you can see through Invisible Bedrock X-Ray effect your Mining Systems.