Floating Continent, FFVI.
It's got Gestahl and Kefka and Ultima Weapon. You have to fight Ultros just to land your airship there. You also run into behemoths and dragons, plus the drama of the escape after fighting Kefka, and the pain of losing Shadow.
I dunno, all the appeal of the Floating Continent is the narrative framing. I don't remember the level design being anything interesting.