There is a bad ass dungeon at the end of FF:AY with a LOT of boss battles the further you progress. The best part about these boss battles as that you may run into enemies from other entries in the FF series. For example, you can fight Omega on one floor, the Phantom Train on another (it even back attacks you!), even Ultros! My favorite of these boss fights was Death Gaze, the Esper you fight in the airship from FF6, and like in FF6, the only way to fight this boss is by running around waiting to fight him in a random encounter.