If we speak to Patricia Tannis in Sanctuary after finishing Bright Lights, Flying City, we can get some new optional missions from her, including the one presented in the walkthrough below, and known as Borderlands 2 Hidden Journals.
In Borderlands 2 Hidden Journals, Patricia tells us about her audio journals, and that she wants them back from where she has hidden them, in The Highlands region.
Patricia Tannis, the antisocial archaeologist, has two habits. Firstly, she records every detail of her various psychoses into audio journals. Secondly, she hides those audio journals out of paranoid terror. She has hidden a set of journal entries in The Highlands and needs you to retrieve them for her.
Experience: 2611 XP
When we travel to the Highlands area, four waypoints will appear on the map, assuming that we have the Borderlands 2 Hidden Journals optional mission enabled. Hence, we have to go to each of these checkpoints to collect the ECHO recordings of Patricia Tannis.
The first one can be found close to Overlook area. We drive near Blake Bridge, and we take the side stairs to go down a level to the maintenance area of the bridge (not the stairs at the base of the bridge). In here we have to get to that small shack, but the door is closed. Because of this, we take an alternate route via the metallic beams nearby.
The second one is a bit tricky to get. First, we need to go to the most northern point on the map. Here, we climb the mountain eliminating the stalkers, and loaders we encounter.
Then we go to the small shack on the water (note that a giant fire thresher might spawn near us). The journal is on the small boat, but its out of the safe zone of the area, so we have to move quickly and also be careful not to drop in the water.
The third recording is at Frothing Creek Mill in the southern part of the region. Its inside the carriage with monster truck wheels, but the door is blocked. Therefore, in order to reach it, we must shoot the two hanging piles from inside to release the door on the other side.
The fourth and final hidden journal is inside Aggregate Acquisition, a Hyperion facility in the center of the map. We need to pay attention from now on, because this area is filled with loaders and combat engineers.
The journal is actually in the electrified room near the bridge in front of us, and in order to reach it we need to take a little detour on the other side of the base. When we finally get near the bridge, a powerful Constructor will spawn. We just have to avoid his rockets and use high damage weapons.
If we get killed, its a good idea to try and eliminate him from below the bridge. After he is defeated, some BUL Loaders (a type of robot with a shield) will appear at the end of the bridge.
We kill them as well, then we drop down where the room with the electrified entrance is, and we shoot the fuse box thats high above us. We loot the chests, we collect the ECHO recording, and then we go back to Sanctuary using one of the Fast Travel points around the Highlands area.
Speaking with Patricia will end the Borderlands 2 Hidden Journals mission and give us the possibility to activate another one, called Torture Chairs. Or, we can go and accomplish additional missions presented in our Borderlands 2 Highlands walkthrough.