Fall down into the hollow and look for a GPS thingee right away. Follow the path, ascend a climbing wall, kill two dudes, and you get a campfire.
When you reach the elevator, push the buttons, then climb on the stack to your right and use the axe on the cog. Then, climb through the elevator to the other side. Climb up to level three, hit the button, then backtrack to find a hatch to break the second cog. Bring the elevator up to level four, the go back to three and look for a ladder that leads to a hatch. Climb up that ladder to reach the third cog. Finally, drop the elevator back down to three. From level four, hit the switch again, then drop into the elevator. Jump out of the hole in the shaft to a climbing wall. That’ll lead you to the fourth cog.
After you drop the elevator, go to the bottom and expect conflict. Then follow the trail to a finding that is both educational and bad ass. Next comes a wave of bad guys but by now you know how to find cover, how to snipe, and how to kick ass. No problem.
Hop up onto the balcony, and follow it to a slide that leads to a climbing wall. When you emerge, you’ll get a call for help. On the outside, there are two guys. Drop them, but don’t go all the way to them, look for a rope on the left. Take that up to the tower, then take another rope down to the beach.