Siberian Wilderness - Through the Bear's Cave to the Exit

Now that the bear is dead, you can enter the cave. Pick more mushrooms in the tunnel on the way in.

Inside the cave, you'll find cloth in a jar to the left...

...and hardwood in a box on the right. You can also finish butchering the bear's kill for hides.

Beyond the dead deer is a document (6/6), Northern Passage from The Hunter series, lying on the ground. Examine it for XP and Russian proficiency.

Then use your climbing axe to pry open the strongbox and obtain a SEMI-AUTO PISTOL PART (1/4).

Finally, approach the weak wall to the left of the strongbox...

...and use your climbing axe to open the passageway to the next level.