Complete the indicated task to unlock the corresponding map. ALL stages can be returned to once you reach act 4 and you are able to return to any of the bonus maps up until you board the ship to the research facility.
Avery Fields: Examine the well at the top of the Church of Restoration during your second visit.
Foreign Quarter: Examine the barrel to your left at the start of the Biruni University stage.
Four Swordsman Spring: Examine the hollowed out tree at the dry riverbed.
Gillbaris Gardens: Examine the skeleton on the opposite side of the central tree from the chest in the Timion Vale mission.
Halls Of Atonement: Examine the king's throne in the Royal Courtyard.
Keliask's Tomb: Examine the glimmering tablet on the ground in the ancient ruins.
Ragnar's Gorge: Examine one of the crates during the mission in Tolby.
Trivishim's Corridor: Use the second mine cart in Dread to open up a cave entrance.
Wanderlust: Complete ALL story and optional battles two times.