With two new Tomb Raider games coming out in the next few years, I wanted to kick-start my Tomb Raider guide series. Please be aware that these might contain spoilers. Be sure to check out my full Tomb Raider project, linked below.
The Soviet Installation is one of the first areas you’ll be given access to in Rise of the Tomb Raider. You won’t be able to unlock everything right away because you’ll be missing gear. In this guide, I will show you which cave to enter to get map secrets. These secrets allow you to know what to look for on the map.
Before you enter be ready to kill some wolves.

So let’s zoom in on the map to see exactly where I am standing.

You want to be behind the large structure towards the right. You can’t miss this cave; it even has space outside of it for you to climb on.

The cave is directly behind me in the image above.

So as you enter the cave, continue going straight inside, but make sure to hang to your left.

Keep going left until you see the image below. There will be some roots blocking the path to the left and a space where Magnesite Ore was growing.

Turn right, and there will be a map on the floor.

Okay, so once you find that, you should make sure to loot the bottom portion of the cave.
Now, to continue in this location because this is part of the Communications Breakdown mission: Go outside and climb the cave. You need to reach the top.

There will be a communications box at the top of the mountain.

After you destroy this, you can zipline down and continue exploring.