To open the gate in the Fortress in 4 – The Western Ghats in Uncharted: The Lost Legacy go down the stairs to the left and grapple around to the to the next building. Climb to the top and turn the wheel to open the gate.
Go back to the gate and go through it. Grapple across to the platform to the right of the building ahead. Go to the back of the platform and make your way around the cliff to the top of it.
To solve the jigsaw puzzle align the shaft of the arrow with the tip for the outer ring so that the shaft points towards you. Align the front of the bow in the middle ring with the outer ring and the same for the inner ring.