The Sabaean Alabaster Stele is the 95 treasure that can be found in Uncharted 3: Drake's Deception.
The Sabaean Alabaster Stele is found in Chapter 21 - The Atlantis of the Sands. It can be found at the start of the chapter, go down the stairs and then to the right. As the staircase wraps around a tower you will see a chunk missing from the left rail. There is a hole here into the tower. Enter and pick up the treasure.