The Nether Portal 'is created by placing Obsidian in hollow vertical rectangle at least 4x5 and then lighting it. It is used for travel to The Nether. The maximum size for a nether portal is 23x23 blocks.
This shows you how to create the normal portal.
- Place a 5 block tall pillar of Obsidian.
- Count two blocks to one side, then place another.
- Make a bridge between the top blocks and bottom blocks.
- Light it with Flint and Steel or Fire Charges.
- Build the full version except the corners
- Use Cobblestone as the corner blocks.
- Light it with Flint and Steel or Fire Charges