On this page of our guide to Uncharted 2: Among Thieves you will find a detailed description of secrets and collectibles available in Chapter 24 - The Road to Shambhala. Our step-by-step walkthrough explains how to find all (3) secrets hidden in the 24th chapter of the main campaign.
The first treasure can be found at the beginning of the chapter, in a chamber with a blue sphere in the center. Collect the item before the cutscene (by solving the puzzle and approaching the aforementioned sphere). The treasure is attached to one of the sculptures that are mounted under the ceiling (shoot at the item to knock it down).
The second treasure can be found after you begin to stroll with Flynn. After making your first jump to a remote ledge, don't make another jump towards the handholds attached to the rock but instead take a look around. In the darkest part of the rock you will find another treasure.
Once you get to the other side of the great hall with the moving bridge, you will reach the stairs. Before you enter the room with a puzzle, turn to the rocks on the left (looking up the stairs). A treasure is hidden there.