Minecraft wiki entry for History, associated text: This file stores all the terrain data that makes up a world. It is comprised of chunks which are 16x16x128 (XZY) block sections of the terrain. It can store a maximum of 1024 chunks (32x32) and 512x512x128 (33,554,432) blocks, however, the game only generates 256 chunks (16x16) and 256x256x128 (8,388,608) blocks by default.