Send seven mails to another player using Mog Net. Then, send four mails through Mog Net to the NPC "The 4 Old Men", and another four mails to "King Alus". It does not matter what order this is done, as long as Alus is last. After reading the fourth one you will unlock the new dungeon. Ride on the Nautulus and go east of the floating continent. Once there you will see a shadow in the water. Go underwater and move into the coral to enter a cave. There is no real dungeon here, but there is a difficult Boss, Iron Giant.
