Minecraft wiki entry for Nether_portals, associated text: The portal choosing algorithm can be used for long-distance travel by manual construction at carefully selected coordinates. If the player has a portal in the Overworld at (0,64,0) but makes a Nether portal at (127,64,127) with its perfect Overworld pair at (1016, 64, 1016), then the portal at (0,64,0) will go to the Nether portal correctly (1-way trip) because it is the only portal available within the 128 search distance along X and Z horizontal axes of the expected Nether portal position of (0,64,0). In about 15 seconds, the player can then travel 1436 meters in the Overworld. This specific form of fast travel by portal is one-way, since the Nether portal will not find this Overworld portal. Given that a railway in the nether would need to span only 180 meters to go this distance, it is usually not worth making such portal links. However, it is theoretically possible to make a one-way ring of portals, with each Overworld to Nether jump going a long distance, but such a ring would easily be disrupted due to the huge exclusion zones created.[2]