I entered a Wizardland through one of the portals found in the dungeon but as far as I can tell there is no exit portal.
I'll double check when I get home but I think not. I always pull every lever and I don't remember any.
If it was a "portal found in the dungeon" rather than a "code found written on a wall that I then entered at the Pocket Dimension", then it's a Mysterious Portal. Sometimes the exit for those will be hidden next to the south walls (where it obscures the ground) or under a random statue/pillar/shrine/etc which may require some Knockback skills to uncover.
