Mountaineering is the seventeenth chapter of Uncharted 2: Among Thieves.
Chapter 17 consists primarily of you following Tenzin through the icy Tibetan caverns. Start by swinging from the rope he throws up and descending the ladder on the other side. Crawl through the tight spaces as you keep following Tenzin as he leads you further into the caves.
After swinging from another rope and having the ground break out from under you while you're on a narrow walkway, position yourself to boost Tenzin up to a ladder. He demands to switch with you so that you can go up instead. Use the rope that's a bit further along to reach the upper level.
Shimmy along the cave walls to continue moving further, jumping and climbing when need be. When you spot Tenzin across a chasm from you, position yourself so that you can catch him when he leaps across. Tenzin gets a chance to repay you shortly after as he pulls you up when you leap across.
After encountering the dead wolves keep heading further, climbing up the cave wall, to reach an open area. As you proceed into the open area an ice formation crashes down sealing you in. Climb up to the upper level and head over to the ladder. Climb down it and grab the pistol nearby; use it to break through the icicles and get back to Tenzin.
As you reunite with Tenzin a Yeti appears and attacks him. Quickly shoot the Yeti repeatedly to draw its attention to you, saving Tenzin's life. Run around to avoid the Yeti's attacks shooting it all the while. Think fast when the Yeti grabs you and press the correct buttons. After you've weakened the Yeti enough, Tenzin steps in and attacks the Yeti thus scaring it away.
After the Yeti scampers off follow Tenzin through the mountain paths again. Leap over a chasm or two to reach the next area.
Keep following Tenzin up the mountain until you reach the stairway which ends the chapter.