The Overworld, as seen in an extreme hills biomeThe Overworld is the starting dimension in Minecraft. As with all dimensions in the game, the Overworld can generate infinitely. The Overworld is limited to 862 by 862 blocks on the Xbox 360 and PlayStation 3 Edition, and 256 by 256 blocks on Old Pocket Edition worlds. At the edge of the Overworld, there is an animated world border. Nether portals in the Overworld can be used to teleport to the Nether.The Overworld encompasses the level ceiling down to bedrock and extending in every direction on the horizontal plane. It is generated through a secret process which creates multiple noise maps to create differing elevations, general chunk shapes, and complex mountain and cave systems.Most mobs in the game can spawn in the Overworld: wolves, bats, pigs, sheep, cows, horses, mooshrooms, chickens, chicken jockeys, squid, zombies, ocelots, skeletons, spiders, villagers, spider jockeys, witches, endermen, creepers and slimes all spawn normally. Zombie pigmen can also spawn near nether portals.Mobs from the Nether may also pass through nether portals and enter the Overworld: zombie pigmen, magma cubes, wither skeletons, ghasts, and blazes (mobs from the Overworld can also enter the Nether through a nether portal). The ender dragon however can't enter the Overworld because there is no return portal from the End unless the dragon is defeated.SeedsWorlds in Minecraft are generated through a procedural formula that takes a random number as a starting point - a seed, and it will be used to generate all the terrain.Using a specific seed generates exactly the same world each time, and thus interesting Minecraft worlds could be shared between players. The spawn is not on exactly the same spot, though, so it is wise to give coordinates instead of directions. The seed input is converted into an integer, so, for instance, the word 'Glacier' corresponds to a value of 1772835215, which generates exactly the same world when entered as a seed value.Many seeds are chosen simply because they spawn the player near desirable resources, a stronghold or some certain special structure, such as a dungeon.SizesIn Classic and Indev, maps can be generated in "small" (128×128×64), "normal" (256×256×64), and "huge" (512×512×64) sizes.In Infdev, Alpha and Beta, maps are somewhat infinitely big − They are made up of chunks; this means that as the player explores the map distant chunks are generated automatically, leading to theoretically infinite maps. In practice, technical reasons (the limits of 32-bit math[1]) force the maximum map size, including the Far Lands, to be around 9.3 million times the surface area of Earth [1], which comes out to about 4.7 quadrillion km2 (The hard limit where chunks are overwritten is at X/Z of ±34,359,738,368, making the world at most 68,719,476,736 meters wide and long, which is about 4,722,366,482,869,645 km2. When compared to Earth's total surface area, 510,072,000 km2, this works out to be about 9,258,235 times that). Whilst the horizontal planes of the maps are vast in size, the vertical plane remains at a fixed (soft limit) 256-block height [2].Map limitationVisual cutoff point of a Minecraft map (Left is normal Minecraft generation, the right is after limitation.)While the map is infinite, the number of blocks the player may walk on is limited. The map contains a world border at +/- 30,000,000 x/z. The world border is an animated wall of blue stripes. As you get near it, the edges of your screen turn red, and you can not go past it. There is nothing past 16 blocks after the wall, just emptiness.Because of these limitations the maximum blocks that can be generated in a world is approximately 921,600,000,000,000,000. This means that a filled world with no entities or tile entities would be 3,686,400,000,000,000,000 bits (409.27261579781770706 Petabytes) in block data alone due to the fact that each standard block is assigned 4 bits of information. The total area of this is about 8 times the surface of the Earth.