Heavenly Sword Ch 3 - Shooting Fish
You will see a whole series of barred gates here. You can shoot your arrows through the barred gates as if they were not even there.
So get ready, because you will have three sets of guards trying to crank open the gates to get to you. Kill them all before they reach you.
If they do somehow manage to reach you, run to the opposite end of the walkway and pop a couple of them. Rinse and repeat until they are all dead.
When all of the guards are dead make your way to the room they were coming from. If there are any gates that they did not open, there are wheels you can turn to open them.
The room that the guards came out of has one more door with a wheel to open it. Exit the room and walk around to the left. Then climb the ladder you find at the end of that walkway.