Minecraft: Nether Portal Hubs
In Minecraft, one of the most efficient ways to travel across large distances in the Overworld is to travel that distance in the Nether. This is because one block in the Nether is equal to (roughly) eight blocks in the Overworld, making it very important for late-game players to build "Nether hubs" and learn how to link Nether portals.
Preparation
Nether portal hubs are essential for any late-game player, especially in single player worlds. They are also very helpful to have on multiplayer survival servers or realms that don't have warps or homes. It's a good idea to build your hub in one of these places:
Just below the Nether roof: Get as close to the bedrock roof of the Nether as you can, then tunnel through the Netherrack to where you need to go. This is the safest option before you can get above the bedrock roof.
Above the Nether roof: This is the safest and best place to put your Nether hub, as long as you remember to spawnproof all the blocks you place. There are many tutorials on how to achieve this, mostly involving ender pearls and a small redstone machine; just make sure you're looking at a tutorial for your version!
You should always center your Nether portal hub on your home portal. This means that you'll need to move that portal to wherever you're building your hub - near or above the roof. To do this, follow these steps:
Go to the Nether using the portal. Make sure to bring obsidian, a pickaxe, and a flint and steel!
Break the portal in the Nether. Once it's unlit but before breaking it entirely, write down the coordinates of the two inner blocks.
Tower up above your broken portal into the Nether ceiling until you reach bedrock.
If you're making your portal above the Nether roof, now is when you would get up there.
Clear out an area in the Netherrack, then place your new portal on the same X and Z coordinates as your old one. When you light and go through this portal, it should link up to your original Overworld portal.
How does it work?
Travelling this way works because one block in the Nether is equal to eight in the Overworld. If you were to build a Nether portal at (0, 0) in the Overworld, go through it, and then build a portal in the Nether at (0, 1000), that second portal would put you at (roughly) (0, 8000) in the Overworld.
Building a "linked portal" - a Nether portal that takes you to a specific spot - is actually fairly simple.
First, travel to the Overworld location you want to link (for example, a stronghold).
Build a Nether portal wherever you want in that location, then stand inside it and write down the X and Z coordinates of one of the two inner blocks.
Light the portal, but do not go through it! If you go through the portal at this point, you won't be able to link it.
Travel back to your central Nether portal and enter it.
Now that you're in your Nether hub, take the coordinates you wrote down earlier and divide each of them by eight, then travel to those new coordinates in the Nether. For example, if you built a portal at (800, 800) in the Overworld, you would need to go to (100, 100) in the Nether.
You can also use a Nether portal calculator for this, like this one.
Once you've reached the coordinates, build your portal exactly on them. The Y coordinate doesn't matter, but you should try to match at least one of the two inner blocks exactly.
Now light the portal you just built and go through it! It should take you directly to the portal you built earlier. This will not work if you didn't light the Overworld portal, or went through it prior to building the Nether portal.