Head up the rocky steps and move over the ledge, then inspect the supply box. Continue underneath the fallen tree and climb up to the right. Follow the trail, climb up, drop down the gap and continue. At the slippery ledges up ahead, you cannot jump-climb. You must grab each ledge carefully, without pressing X.
After the cutscene, continue and climb up the big rocks. Before jumping over to the rocks with small streams of water falling down from them, look to the right for a lower platform. Jump to it and from here to the ledges up ahead. Continue all the way to the right, go around the corner, and then up. Before you climb all the way up, though, check the crack to find Treasure #66, Persian Ring.

Climb up, make your way through the small cave and continue climbing up to the platform with a tree on it. Use the rope to swing to the platform next to the ledges up ahead, and climb these to proceed. Move around the side of the rocks until you reach the top - a short scene will play. Attack the rope to the tree and drop down, then gently climb and drop down to the ledge below. A few meters ahead, on the left wall amongst some small bottles and cups, search for Treasure #67, Wood Tankard.
Continue down the trail, jump to the right side, then from here to the platform in the middle, from where you can jump to the path further ahead. Look for the skeleton in this mossy area for Journal Entry #15. Slide down the gravel hill, climb the ledges and go inside the river cave. To the left side you can find Treasure #68, the Spy Glass. Continue through the cave's small tunnels and go outside.

Climb up and check the skeleton to the left for Note #7. Look up at the skeleton hanging high up to jot down Journal Entry #16. Climb up the ledges and collect the Piton along the way, which allows you to climb weak rocks. Climb up, jump to the grassy platform and from here towards the (weak) rock wand on the other side, using the Piton to hang on to it. Go up and then to the left. Leap to the ledges, go right and you'll run into some mercenaries.
The plants/tall grass allows you to move unseen. A detailed step-by-step walkthrough for this segment will be available soon, but for now it suffices to say that you should remain undetected for as long as you can, pushing forward through this area. When you do end up in a firefight, it doesn't really matter. You can always replay this section later on to try and go through full stealth.
You'll eventually reach a more quiet portion of the forest again. Go past the enormous tree and climb the platform to find a skeleton. He holds Note #8. Climb the walkway to the left and head to the far left of it to find Treasure #69, Dress Dirk at the end in the darkness.

You will meet up with Sam soon enough. Continue over the fairly linear path until you can climb a turquoise-ish platform/small roof and drop down in a building. Crouch-walk through the tunnel, move underneath the crate. Instead of going left, turn right. Go through the hole in the wall, continue down the tunnel, then go right through another hole in the wall and drop down. Move right to go underneath the wooden floor and walk to the end. You can find Treasure #70, Frechen Bearded Bottle among some crates here.

Finish the chapter by making your way through the rest of the building's linear path.