Minecraft wiki entry for Far_Lands, associated text: If you tried to make a nether portal at the Nether Far Lands, you would end up at ±100,406,560 X/Z, which is impossible, because beyond 32,000,000 at the Overworld, blocks stop generating and "fake blocks" will generate. You can't edit the terrain beyond ±32,000,000 X/Z, so the Nether Portal can't appear past this point. This is a dangerous but faster method then walking from the overworld.