Minecraft wiki entry for Nether_hub, associated text: To access the real nether without having to find a trapdoor on the roof every time, you will need to relight the portal you broke in the first step. Travel through it to get to the overworld. Dig down below the existing overworld portal, or make a platform above it and light a new portal. Now the upper portal should link to the Nether roof and the lower one should take you to the actual nether. Repeat as necessary.