Looks like the PS4 vs Xbox One battle is turning one-sided as far as sales victories are concerned....
Tomb Raider Previous Inhabitants Challenge Guide – Cliffside Bunker Flags Locations
This challenge is found in the Cliffside Bunker of Tomb Raider and is very similar to the Non Believer challenge. Again, you simply need to find four banners/flags and burn them using your fire arrows (fire arrows are important as one flag is completely out of reach). Here’s where to find them:
Flag #1: Coordinates – 712558, 3415924
Location. At these coordinates you will find a room with a large WW2 era cannon. The flag is on one of the walls here.
Flag #2: Coordinates – 712566, 3415931
Location. In the main room where you get attacked by a large group, look on the wall above where you enter, and you can find it high up.
Flag #3: Coordinates – 712563, 3415930
Location. This is on the roof of the building where you find the last one. Check the walls.
Flag #4: Coordinates – 712564, 3415928
Location. This one is a bit tricky. Stand on the roof and look at the large metal tower/crane nearby (the one with the thick wires). The flag is high up on one of the beams.