You find the entrance to the tomb after you leave the village towards the river and jump over several platforms. You will get to a gate that you need to walk around, through the passage under the rock. Right afterwards, you will be attacked by several wolves, so prepare your weapon beforehand (you can also find a Survival Cache here).
Walk inside and follow the corridor squeezing between rocks. A bit ahead, you will walk into a camp (Lara comments on the architecture here, in the passage, you walk by a Relic, and you can jump down, before you enter the passage and pick up a Survival Cache next to the well). In the camp, there also is a Document. Walk into the yard across the passage opposite the campfire.
At the other side, you can find a Relic and Survival Cache under the stairs on the right (optionally, enter the water, into the basin on the right, where you can dive and swim into a separate location - here you find an Explorer Satchel and a Survival Cache). Then, approach the enclosed hole in the ground, in the left corner of the yard (the screenshot). Jump down and connect the platform with the hanging element. Return to the yard and find the cart on the right. Give the cart a push, as strong as possible.
While close to the cart, look up, towards the bucket hanging above. To its right, you spot a lever - take a shot towards it and approach the cart quickly. The bucket will fill with water and will come down, for a moment. You need to fit within this time window and shoot towards the bucket to attach the rope. Be quick about it, because the bucket goes back up after a while.
Finally, climb up higher, over the stairs and jump over to the successive platforms to get to the chamber at the other side. There, you find a book and an Archivist Map, a well as a Document on the railing, right next to the entrance.
Reward: Ability "Fast Healer" (faster dressing of wounds).