Dungeons are optional places you can visit throughout the game, either to help gain some more experience for your characters or even find some treasure. Similar to missions, each dungeon is broken up into separate rooms, where you will usually face a certain amount and type of enemies. Each dungeon has a specific level range for the monsters that reside in it, so it's a good idea not to venture inside them until you're ready.
The following pages will list every single dungeon in the game, with them listed in order of the monsters' levels inside them. A room-by-room breakdown will be shown, as well as what you can grab from the treasure chests. Dungeons can be blocked off until you gain access to an area, with some of them (Tower of Agito and Valley of Monsters) actually requiring you to get the Setzer airship first.