Halatali Access Question

[Niwashi]

It's worth occasionally checking each area for the blue quest icons with the little plus sign in the lower left corner. That icon indicates that, even though it's not part of the main scenario, the quest is still significant for unlocking something. Some, like in this case, unlock extra dungeons. Others might unlock a game feature (like mounts, materia melding, the Gold Saucer, or there's many others).