When done, the Nether has the same 256×256 borders as the Overworld, and if a nether portal is then made in the Nether, it can spawn the player outside the world barrier. The portal block must be placed using cheats. In the former Old‌ world type, it is impossible to construct a nether portal. Any of the blocks in the corners can be destroyed without destroying the portal. The portal can be destroyed by breaking the obsidian frame, by a nearby explosion, or by placing water in the Overworld or lava into it with a bucket or dispenser. If there is no corresponding portal, a new 4×5 portal is created. The portal plays a sound effect while the player is inside it. The player can step out of a portal before it completes its animation to abort the teleport. In Survival, the player must stand in a nether portal for 4 seconds to get to the Nether. The portal allows most entities (with the exception of the wither, the ender dragon, and entities riding or being ridden by another entity) to be transported to a corresponding portal in the Nether.

Once the frame is built, it can then be activated by placing fire within the frame, using flint and steel, fire charge, dispensers or any material that is capable of igniting fire.

To create the portal, the player must first build a rectangular obsidian frame, ranging in size from a minimum of 4 blocks × 5 blocks to a maximum of 23 blocks × 23 blocks. To access the Nether, the player must construct a nether portal in the Overworld (portals created in the End do not activate). 'Economy' portal without corners (left), full portal (right)

Minecraft nether castle map