I made a portal maze as one of the last quests in my upcoming Quest Pack "Heir of the Cursemaster".
Basically, a bunch of doors lead to other parts of the dungeon instead of to the next room over.
The Heroes have to navigate the door maze, find the secret doors that let them get around to the back side of the portals, and find both the exit portal and the mirror housing the item that lets them go through it.
Additionally, there are a few doors which curse the Heroes if they pass through them - so they can take what looks like a shortcut if they want to, but it may be costly!
I'll put up an image of the Quest layout later tonight.
Edit: Here we go!

The Heroes start in the room with the spiral stairway and must make their way to the center room to use the large portal there - but first must visit the mirror in the upper-right quadrant, otherwise that portal will not work.
Gray doors work like normal.
Passing through a blue door takes you through to the door with the same number on the same side (white or black arrow) as you entered.
Orange (trap) doors can also be passed through as normal, but will curse any Hero who moves through one! Probably there should be one or two more of these somewhere but I haven't decided where yet.
Oh, and one more catch: when the Heroes get the item from the mirror, all portals and curse doors stop working and become regular doors, necessitating a different route to get back to the middle room!