Soviet Installation - Ancient Cistern Challenge Tomb (Part 2)

After examining the relic, climb the stairs to a landing overlooking a small pool.

Jump to grab the horizontal beam...

...activating a mechanism with 2 large gear shafts directly below. This mechanism lowers the water level but will also kill Lara instantly if she gets caught in it.

Wait for the gears to turn so there is a gap between them. Then press B to drop into the pool below.

Climb out of the water on the left and pick up up 2 Byzantine coins.

Then swim across the pool and follow the passageway around to the right, collecting some cloth from the container in the corner.

Take the arrows leaning against the wall...

...and shoot the red oil can...

...to blow open the wooden door.

Wade along the flooded passageway to the Cistern Cavern Base Camp.

From the campfire, head down the stairs to the main room, a huge cistern. Lara spots her goal: a codex on a lectern sheltered by an ancient dome.

Scramble up onto the elevated walkway, turn right, and move to the end.

When you try to grab onto the rickety planks on the wall below the dome...

...they collapse, dropping Lara into the pool below.