You obtain a key item to open them later in the game.
Ohhhh okay. Thanks. Was running all along the edges of these dungeons looking for a secret passage to get a key. lol
One more question... what is with the support abilities that increase that job's weapon proficiency to S? When that weapon is usually already at S. Can you cross-class support abilities later on? Or do some jobs not have an S scaling in their primary weapon?
Black Mage for example got Rod lore (think that is the name) and they already have Rods at S.