How to create a giant minecraft portal

First you need to find a clear space in you world like I have

To make the portal you will need obsidian and flint and steel

Dig one block down in a straight line to make a base.

Add in obsidian into the ditch

Then stack the same blocks 10 blocks high.

Do the same on the other side.

Add blocks across the top to make a rectangle.

Select flint and steel and press on the bottom right hand corner with the flint and steel.then you portal should appear.

Tip:In the nether never lose your portal or you can't get back the the overworld.