Minecraft wiki entry for Overworld, associated text: The Overworld encompasses a three-dimensional volume that extends vertically from the Void up to the build limit (y=−64..320), and horizontally for a virtually infinite distance in each direction. This volume is filled (virtually speaking) with air, terrain, and structures. Technically, the terrain is formed by generating multiple noise maps to produce differing elevations, general land shapes, and complex mountain and cave systems.