Among these collectibles, is a Strange Relic, that will earn you ‘Relic Finder’ trophy when you retrieve it. It’s not that hard to spot, but you can easily miss it.
It can be found in Chapter 15. You will come across it when Drake would jump across a huge gap to open a wooden door for Marisa. She would try to open the door but won’t be able to.
Now, you would need to make way to the other side of this door to open it for her. This is the spot you need to look for the Relic; you can do that before or after opening the door. It is just by the wall close to the door. You will need to climb up to the top to reach the relic.