The Antique Pipe is the fourteenth treasure that can be found in Uncharted 2: Among Thieves.
The Antique Pipe is found in Chapter 2 - Breaking and Entering. As soon as you gain control of Drake after Harry's betrayal, you can immediately grab another treasure. It makes sense, after all -- you're in a museum exhibit. If you were finding treasures in sewers, you're going to find them here! You'll have to act quick, though, because the guards' lethal weapons will be pointed at you immediately, and their red laser sights mean death for you. The area you're going to want to look in, is an alcove on the outer edge of the room with what appears to be a concrete lion's head of some sort. There are multiple lion heads, so you want the one closest to you when you gain control (the one to the left of the guard behind the gate). Go towards this alcove and quickly acquire your treasure.