Follow the only possible path and approach, after a while, the area where you will meet, for the first time, apart from the regular enemies, martial artist. They are pretty demanding. You need, first of all, be prepared that they can break some of your attacks and, in such a situation, do not allow them to land their own blows. What is more, they often perform two hits in a series so, it pays off to be prepared to press the counter-attack button twice.
It is best to start the fight with the abovementioned enemies by gliding towards one of the martial artists, although you can, just as well, use one of Batman's gadgets. While fighting these enemies, do not let yourself be cornered, especially that the arena is not too big. After the victorious battle, locate the weakened point in the wall and blow it up, using the explosive gel. Go ahead, and reach the door leading up to the Sewers - Water Treatment.
[New Character Trophy: Martial Artist]
[New Challenge: Custom Challenges]
[New Challenge: Combat Training]
Start by using the hook on the ledge located on the left. You can jump to reach the next ledge (the above screenshot) so, in this case you do not need to use any gadgets Turn to face the enemies on the right and pull yourself towards the platform which they occupy. Grab the opponent that is standing closest to the edge and climb to deal with his colleague in a more traditional way.
To continue climbing, you need to use the hook on the side ledge shown in the above screenshot. Shimmy to the right to reach another ledge. Wait for steam to stop leaking and resume shimmying. After you get to the control room, start by pressing the big red button.
Turn to the big pipe that you can see in the distance, which is leaking steam. Select the claw from the inventory and aim it at the manhole on the left, which will result in its opening. Note that performing this action held steam leakage, You can now use the grapple and extend the rope Of course, you need to catch onto the rope using the hook and allow the Batman to zipline, which will end in tackling down of the enemy occupying one of the upper rooms.
Take a look around this room to find the control panel and hack into the system, using the Cryptographic Sequencer (the above screenshot). Hacking into the system will result in unlocking the grate that you have passed by earlier, at which there is another enemy. Glide towards this character, knock him down and finish him off before he regains his strengths. You may now open the door leading up to the GCPD Telecom Room.
Go North and after you reach the edge, position yourself opposite the enemies that are staying on the large elevator. I recommend that you attack the enemies by surprise, either by gliding towards one of them, or by throwing them some gadget, like the concussion detonator). Regardless of which you choose, try to eliminate the martial artist as quickly as possible and deal with the remaining enemies only then.
Approach, carefully, another group of enemies and, just like earlier, take advantage of the fact that they are oblivious to Batman's presence, at first. While fighting, watch out not only for the martial artists, but also for the overgrown bandit. Just like in the case of the fight in the precinct prison, try dodging this bandit's charges and do not let yourself be grabbed by him because you will unnecessarily lose some of your health then, and additionally, you will have to free yourself. To deal damage to this enemy, use the quick combo preceded by the cape stun. After you finish the fights, approach the control panel and upload the data to the bat-computer.