The Tibetan Square Ghau is the eighty-seventh treasure that can be found in Uncharted 2: Among Thieves.
The Tibetan Square Ghau is found in Chapter 23 - Reunion. Located just before the puzzle with the shapes and Tibetan letters. (Obviously a helpful tip before you get there). As you swing on the bits of wood hanging over the building you will climb through a window and jump over to where there are some wooden cases. As you climb up and onto the roof, walk along the wooden beam onto the roof. Go to the corner and hang off, there you will see a statue with the treasure.