In Final Fantasy for the iPhone and iPod, there are some secret areas you can unlock by performing specific tasks.
To unlock the Labyrinth of Time secret area, you’ll need to defeat four bosses. You’ll need to beat Lich in the Cavern of Earth, Tiamat in the Flying Fortress, Kraken in the Shrunken Shrine, and Marilith in Mount Gulg. Once these are beaten, visit the Chaos Shrine to gain access to the Labyrinth of Time.
Beating all of these bosses will also gain you access to the other four secret areas as well.