Is it possible to create a portal larger than 2x3 to the Nether?

Can one create a fully functional 3x3 portal? (That's 3x3 on the inside, and 5x5 on the outside)

If you're wondering why I would want to do such a thing, it's purely for aesthetic reasons. I have a room with a wall 3 wide built deep within my base and it would be more trouble than it is worth to resize the room. Hence a 3x3 portal would be perfect.

Solution 1:

As of snapshot 13w37a, you can now create portals of any size between 2x3 and 21x21. This is a feature in Minecraft 1.7.

Solution 2:

As of Minecraft 1.5_01, only 2x3 portals can be created (via Obsidian frames) to provide transport to the nether.