Glacial Cavern - Cavern Entrance and First Document

Move forward to a steep drop-off. You could take a running jump forward and attempt to latch onto the ice wall, but it's not strong enough to hold Lara's weight.

To save her from a minor fall, instead just drop down into the tunnel below on the left. (Avoid the deep chasm on the right.)

Slide down the slope.

Then turn around. Above on the right is where you came in. Climb the short ice wall on the left.

On the ledge above is a document (1/4), Shores of Svetloyar from The Hunter series, which confers Russian proficiency as well as XP. The climbable wall on the other side of the gap leads back to the start.

So turn around, drop down, and follow the tunnel down into the cavern.