Arkham West / East - Batman: Arkham Asylum
As you enter this area you get the Riddle: “Does the Scarecrow's gas break down barriers as it drives you insane?”
Ahead of you is a weakened wall – pull it down, then walk to the edge and scan the area with Detective Mode to get an idea of what you face below.
Glide down and take out the sniper in the tower – if you do it right you can literally glide down and fall right on top of him. You get a mini-Ivy CS then, telling you that the Island belongs to her. If you look around there are quite a few pods here as well, so let us take these out now.
When you reach the pod near the Gate to Arkham North, go through the gate – there is another pod to kill here – then zip up to the ducts above and target the weakened wall – zipping up there and grabbing the Riddler Trophy which unlocks yet another challenge.
After you take down the pods near the gate to Arkham East, zip up on the bean there and pull down the weakened wall above, zip up and scan the pair of gas canisters to solve the Riddle for this area! Drop down and walk towards the gate and look up to spot another weakened wall – pull that down and zip up there to grab another Riddler Trophy and pick up the Achievement: 'Mental Athlete' for (20 GP).
Now drop down and head through the gate.
Take out the two pods ahead and you get your next upgrade – I chose the Triple Batarang myself. Now continue on and zip over the locked gate, taking out the pod on the other side, and then rinse and repeat and head through the gate into Arkham East.
Another warning from Ivy, more pods, and you are going to want to take out the snipers first. Move to where you can zip up to the nearby guard tower and do that, then take out the sniper here with a ninja-kill. When the far sniper looks away run along the catwalk to the guard control area at the end and loop around behind him out the other end, sneak up and do another ninja-kill.
As we are right beside the entrance to the Botanical Gardens, you may as well zip up to the roof of the guard tower we are in and then glide down to the door and enter.