Dream Sequence - Excavation Site:
Head down the hill, on the next screen there is a Draw Point for Sleep. Head forward and you will be ambushed by Esthar Soldiers; after the battle, head to the left path.
In the next room, there is a Draw Point for Confuse to the right and a ladder at the end, go down the ladder.
In the cave, interact with the debris to the left to find an "Old Key" but Laguna will drop it immediately. On the next screen, interact with the middle panel to set a trap; this will be useful later on. Before leaving, interact with the right hatch as well, nothing will happen now, but will pay off later.
Head east and keep going, eventually you will arrive at a platform leading south to a ladder, climb the ladder and you will be back at the beginning where you were ambushed. Go back through the way you initially went (left path, down ladder etc.) and interact with the left hatch then go back the way you came (west, up ladder, south, take right path, down ladder and north).
Entering back into the cave, at the bottom of the screen is a pile of debris; interact with it to find the last "Old Key", which Laguna will also drop.
Take the north route and then head west, past a boulder. On the next screen, you will find another boulder and a device on the floor. You can blow up the explosives to move the boulders; you will want to do them in this order: Red then Blue. Doing this, plus tampering with the other hatches earlier, the explosions will shake the hatches loose and doing it in this order prevents the boulders from blocking your path.