Copper Mill - Red Mine Challenge Tomb (Part 4)

While you ponder the mine cart puzzle, make a few pickups. When Lara drops from the bucket, she lands on the lower ledge. Return up the stairs.

At the top, turn around to spot a relic (15/18) sitting on the crate. It's a Bomb Fuse for an improvised explosive from the Gulag Possessions set.

In the little room to the right of the room with the codex, there's a Russian document (22/26), Discovery from The Red Mine series, and locker with some salvage and arrows inside.

Run up the wooden ramp to reach the ledge above and to the left of the staircase.

Turn around and use the horizontal pole to swing across to the ledge above the room where you found the document.

Examine the mural (10/12) on the right wall to gain XP and increase Lara's Russian proficiency. (I think this one is All Empires Fall from the Soviet Crests series.) Now climb up on the left...

...so you're on the roof of the room with the codex, overlooking the buckets and mine cart track. Shoot a rope arrow into the mine cart at the top of the track to pull it out from behind the barrier.

The cart then rolls down the track until it is stopped by the dangling bucket. Move around to the right.

Stand near the rope-wrapped post and turn away from the open room. There's a small crawlspace at the back of the room. If you follow it to the right, you'll find a container with some cloth and a gold coin.

Return to the main room and stand next to the rope-wrapped post.

Then shoot a rope arrow into the mine cart you just freed.

Lara automatically anchors the rope, tethering the cart to the pole.