Enter the Valley
Lara leaves the caves behind and comes out into the light. She’s currently in a massive valley that is filled with steam vents. In the middle of Siberia she’s actually going to be sweating instead of shivering. Her next objective is higher in the area, so some climbing is warranted.
Turn left and climb a series of dilapidated stairs. They take Lara to a zip line. Slide down that, and watch a scene at the bottom.