Minecraft wiki entry for The_Nether, associated text: To access the Nether, the player must construct a nether portal in the Overworld (portals created in the End do not activate). To create the portal, the player must first build a rectangular obsidian frame, ranging in size from a minimum of 4×5 to a maximum of 23×23. Once the frame is built, it can then be activated by placing fire within the frame, using flint and steel, fire charge, dispensers or any material that is capable of igniting fire.