Minecraft wiki entry for Defeating_a_Nether_fortress, associated text: When you create your nether portal near your spawn point in the Overworld, your original nether portal will be close to the world center in the Nether. This might be hard to understand, but the Nether is divided into several hundred block wide regions, each containing either a nether fortress or a bastion remnant. Four of the closest of these regions surround the center of the Nether, on the northwest, northeast, southwest and southeast directions. You preferably want to find a close nether fortress, so you can revisit it whenever you need more blaze rods and wither skulls. So you want to check out each of these four regions to know if a fortress is in there or not. If you see a bastion remnant, you can guarantee that there will not be a fortress in the same region. At this point, turn around and search another region, until you find a nether fortress.