In Chapter 4, you need to climb the tower in the middle of the map. After you open all 4 doors at the top, don't touch the crank in the middle. You climb up the door to the left of the Bow door, and you will notice that it is a little broken, allowing you to climb it after it is open. Climb to the top of the tower, and stand there for a few seconds until Chloe goes through all of her lines and begins doing yoga on top of the tower.