Be mindful that this area would be cutoff after your fight with Egil at Agniratha. Your objective is to reach to the top where the Central Factory entrance would be.
Points of interest in unlocking the whole map: There's an elevator that takes you to the ground floor. After you unlock the circular shape stairs on the second floor. At the green traffic light area, jump at the far right area to land on the spent fuel tank area you saw on the right side of the ground floor area. The last point of interest is after you unlock the large door which takes you outside, go on two vents. Then go on the right side until you reach the down slope area. Jump down to the second area where the tunnel is that will take you to a secret area which is the Machina Refuge. Remember to stock up for better weapons and do the remaining side quests for this area.
When you reach the top of this section, after a long run, you'll encounter Galdot in his suit with his memory totally erased at this moment. For this battle, you'll continuously encounter a future event in which any of your team gets paralysed. Take care of enemies at each cover until you reach Gadolt. Eventually Gadolt thought to have destroyed you with Vanea guiding you and for the first time, it's Lady Meyneth's soul that saved everyone.
At this point, both Sword Valley and Galahad Fortress is now inaccessible.