Soviet Installation - Ancient Cistern Challenge Tomb (Part 3)

Swim around the spike-topped fence and through the arched opening in the southern corner.

Follow the passageway to a small room with a round, wooden door that has water leaking in around its edges.

Pick up more arrows and a red oil can at the top of the steps.

Toss the can onto the ledge by the door. (LT to aim, RT to throw.)

Then shoot the can...

...to blow open the door, flooding the room.

Swim through the door you just destroyed and follow the passageway back to the main room.

Swim across the pool and climb the stairs.

Here you'll find a bunch of arrows, a box of supplies in a raised alcove, and several red oil cans.

Pick up one of the cans...

...and toss it onto the wooden platform floating in the far right corner of the pool.

Now go up the stairs or scramble onto the ledge to the northwest. There's another raised alcove here, where you'll find a container with cloth and a gold coin, plus a document (7/26) written in Greek: Correspondence from the Ancient Cistern series. Hang from the edge of this alcove and climb/jump along the ledges to the right until you can pull up into another alcove.

This one contains a stack of gold coins and an Archivist Map (2/9), which reveals the locations of relics and documents in this area on your map.

Drop down from the alcove, climb the stairs, and then jump to grab the horizontal beam.

Doing so opens a sluice gate off to the right. The rushing water sweeps the platform with the can across the pool, past the round, wooden door, toward the water wheel in the far corner.

When the beam reaches its lowest point, drop down, draw your bow or pistol, and aim in the vicinity of the round door.

As the water recedes, the platform floats back to the right. When it passes in front of the door, shoot the oil can...

...to blow up the door.

More water flows in through this opening, further raising the level in the cistern. The platform survives the blast and returns to its original position.