Successfully complete the game on the Normal or Hard difficulty to unlock New Game Plus mode. This mode allows you to keep your previously earned gadgets and experience points. Additionally, there will not be any counter icons on thugs, thugs and Bosses will be more difficult, and thugs will have different configurations.

Note: The alternate ending requires the bonus "Catwoman" downloadable content. In Catwoman"s third mission, when you have the option to go left or right with the "loot", go right to view the alternate ending. You will still be able to go backwards and not ruin anything in the main campaign.

Use Batman"s Cryptographic Sequencer to go to the following coordinates to intercept secret radio broadcasts that read numbers, make a buzzing sound, and then repeat the numbers again. When the numbers are matched to the corresponding letters of the alphabet, they spell out a hidden message. Note: Some of the secret broadcasts may not be available until after completing the main campaign.

Hidden message 1

Location: X: 700.00, Y: 500.00
Message: 9-23-9-12-12-18-5-20-21-18-14-2-1-20-13-1-14
Decoded message: "I WILL RETURN BATMAN"

Hidden message 2

Location: X: 500.00, Y: 900.00
Message: 5-15-9-7-21-18-18-14-3-5-24-15-12-7-22-3-10-5-15-9-22-3-8-25-26-15-16-25-10-15-17-25
Decoded message: "YOU WILL PAY FOR WHAT YOU HAVE DONE TO ME"

Hidden message 3

Location: X: 200.00, Y: 500.00
Message: 3-20-26-18-26-16-24-1-11-4-24-9-3-8-5-2-12-18-6-16-7-11-3-10-17-5-13-4-21-8
Decoded message: "FEAR WILL TEAR GOTHAM CITY TO SHREDS"

Alternate throwing the Batarang and evading or jumping over the heads of enemies until you get to do a special move (combo 5x or 8x). You can do this five times before it will not add to your multiplier. If it gets blocked, it should not break your combo. It seems throwing Batarangs in succession also works well, as you can throw at least two at a time, and it will not break a combo. Additionally, jump into the middle of enemies, and perform the Bat Swarm.

Go to the manager"s office inside the Steel Mill. On the floor, next to the Harley Quinn costume, there is a positive pregnancy test.

In the Warden"s Office in Batman: Arkham Asylum, go back to the room with the Warden"s portrait on the far wall. Turn left as soon as you enter the doorway, and approach the wooden wall. You can destroy it with Explosive Gel. It may take a few tries, but one of the panels on the wooden wall can be destroyed. Beyond the wooden wall is an unmarked room with a blueprint on the wall. It shows plans for the relocation or expansion of Arkham to Gotham City. This is a reference to the setting of Batman: Arkham City.

After you defeat Ra"s al Ghul and are leaving the subway tunnels, instead of going the correct way, backtrack until you find a gate blocking your path. You should see a button on the far wall and a gap in the iron bars. Throw the Batarang through the gap to hit the button. There will be a cutscene with Killer Croc. Note: You cannot reach this area again after this point in the game.

During the second visit to the Steelmill, you will see The Joker on the large TV. He will start talking about TV shows, and say "How come it all ended in a church," which is a reference to the TV show, Lost.

Note: To access this secret room, you must have the upgraded Cryptographic Sequencer with the "TYGER" codes installed. Just north of the Industrial District in the Harbord, glide onto the Falcone boat west of the two cranes hanging over the water -- where you do the first set of Augmented Reality challenges. Use the Cryptographic Sequencer to hack the door on the boat. Enter "CityofTerror" as a password to open the hatch on the boat. Inside are a bunch of containers with cockroaches on them and a dead inmate. There is also a shipping invoice for Dr. J. Crane (Scarecrow"s real name), hinting that Scarecrow did survive the Killer Croc encounter.

Towards the end of the game, you will get the "Heart Of Ice" side mission from Mr. Freeze. You must find Nora Fries to complete the quest. Go to the Industrial District in the south-eastern part of Arkham City. You should see a marked area of Nora"s estimated location. There is a well guarded building with a locked front door. When standing in front of this building, fly north, and land on the ship. Use the Freeze Blast on the water to create a sheet of ice. Use the Batclaw to navigate to the destroyable wall, and use the Explosive Gel to get inside the building. Defeat the guards, and return to Mr. Freeze to get the "Bargaining Chip" trophy.

You must throw a remote controlled Batarang at the Mystery Watcher to get the "Catch" trophy. After rescuing Catwoman in the courthouse, exit the courthouse, and you should be able to see the Mystery Watcher across the street, on top of the building to your right. Simply throw the remote controlled Batarang at him, and he will automatically catch it, and you will get the "Catch" trophy. Note: You cannot get the "Catch" trophy after completing the Mystery Watcher side quest.

Successfully complete the main campaign to gain access to the "Restricted Area" at the center of Arkham City. You will then be able to climb the Wonder Tower, which is the tallest point in Arkham City. Climb it, jump off the tower, and glide towards the Church. You will eventually hit the invisible barrier between Arkham City and the restricted zone, and Batman will automatically turn around. To keep Batman gliding, simply turn around to hit the invisible barrier again and automatically turn around, lifting Batman up to continue his glide. If you keep turning and hitting the barrier, you will always remain in the air, and will get the "Gotham Base Jumper" trophy after one minute.

The Mystery Watcher appears after the following specific events in the main plot:

1. After leaving the building where you saved Catwoman.
2. After meeting The Joker for the first time; he is on the Ferris Wheel.
3. After interrogating the Major.
4. After saving the reporter.

Scan the Hyroglyph each time after talking to the Mystery Watcher and he disappears. After scanning all four Hyroglyphs, the final location of the Mystery Watcher will be revealed. Note: If you miss any of these locations, you can still find the Mystery Watcher in these locations after completing the main campaign.

To find Crime Alley, go south from the Church. The alley is just below the letters "Restricted Area" on your map, and behind the Monarch Theater. In the alley, look for a lit section of concrete where two fresh chalk outlines have been drawn. Some flowers are laid down, with a note from Hugo Strange, and a tape. Stand near the red rose, and interact to kneel at the site of Batman"s parents" murder and get the "Pay Your Respects" trophy. You can also take the tape left by Hugo Strange.

Perform the following moves in a combo to get the "Perfect Freeflow 2.0" trophy:

Combo Batarang
Stun
Strike
Counter
Aerial Attack
Ultra Stun
Special Combo Takedown
Special Combo Bat Swarm
Special Combo Multi Ground Takedown
Special Combo Disarm and Destroy
Ground Pound
Beatdown Finisher

Visit Calendar Man on the following twelve dates after rescuing Catwoman to get the "Story Teller" trophy:

Jan 1st
Feb 14th
Mar 17th
Apr 1st
May 8th
June 19th
July 4th
Aug 16th
Sept 5th
Oct 31st
Nov 24th
Dec 25th

To easily get the "Story Teller" trophy, disconnect the internet connection to your PlayStation 3. Then, set the system date to each of the indicated dates and visit Calendar Man. Calendar Man is located in the basement of the courthouse. When you speak with Calendar Man on one of the indicated dates, he will tell you a story about the current month"s holiday, and then tell you to return during the next month"s holiday. Save the game by leaving the building. The calendar on the wall next to his cell will highlight the holiday dates for the current year and scribble out which months you have already spoken to Calendar Man about.

Successfully complete one of the following tasks to get a trophy:

Platinum (Platinum): Unlock all other trophies.
I"m Batman (Bronze): Become the Bat.
Acid Bath (Bronze): Save the damsel, but is she in distress?
Savior (Bronze): Save the medical volunteers.
Chimney Sweep (Bronze): There is only one way in.
One-Armed Bandit (Bronze): Hammer the point home.
Communication Breakdown (Bronze): Clear the airwaves.
Gladiator (Bronze): Last man standing.
Wrecking Ball (Silver): Stop the unstoppable.
Lost And Found (Bronze): Uncover the secret of Arkham City.
Sandstorm (Silver): We are legion.
Hide And Seek (Silver): A deadly game of hide and seek.
Ghost Train (Silver): Fight for survival.
Freefall (Bronze): Don"t look down.
Exit Stage Right (Silver): All the world is a stage.
Forensic Expert (Bronze): Collect enough evidence to locate the gun for hire.
Contract Terminated (Silver): Stop the contract operative.
Serial Killer (Silver): Track down the serial killer.
Mystery Stalker (Bronze): Reveal the mystery watcher.
Distress Flare (Bronze): Answer the call for help.
Broken Toys (Silver): Destroy it all.
Ring Ring (Bronze): Answer a ringing phone.
Dial Z For Murder (Silver): Stop the phone booth killer.
Stop the Clock (Bronze): Time is running out.
Bargaining Chip (Bronze): Reunite the separated couple.
AR Knight (Silver): Complete all augmented reality training exercises.
Fully Loaded (Bronze): Collect all of Batman"s gadgets and upgrades.
Aggravated Assault (Bronze): Stop all assaults in Arkham City.
IQ Test (Bronze): Solve the first riddle.
Conundrum (Bronze): Rescue the first hostage from Riddler.
Mastermind (Bronze): Rescue the second hostage from Riddler.
Puzzler (Bronze): Rescue the third hostage from Riddler.
Intellectual (Bronze): Rescue the fourth hostage from Riddler.
Brainteaser (Silver): Rescue the fifth hostage from Riddler.
Genius (Silver): Rescue all the hostages from Riddler.
Bronze Revenge (Bronze): Obtain 24 medals on the original Arkham City ranked maps (as Batman).
Silver Revenge (Bronze): Obtain 48 medals on the original Arkham City ranked maps (as Batman).
Gold Revenge (Silver): Obtain all 72 medals on the original Arkham City ranked maps (as Batman).
Campaign Bronze (Bronze): Obtain 36 medals on the original Arkham City campaigns (as Batman).
Campaign Silver (Bronze): Obtain 72 medals on the original Arkham City campaigns (as Batman).
Campaign Gold (Silver): Obtain all 108 medals on the original Arkham City campaigns (as Batman).
Flawless Freeflow Fighter 2.0 (Bronze): Complete one combat challenge without taking damage (any character).
Twice Nightly (Silver): Complete New Game Plus.
Gotham Base Jumper (Bronze): Jump off the tallest building in Arkham City and glide for 1 minute without touching the ground..
Pay Your Respects (Bronze): A moment of remembrance.
Storyteller (Bronze): Have 12 murderous dates with Calendar Man.
Catch (Bronze): Find someone to play remote Batarang catch with.
50x Combo (Bronze): Complete a combo of 50 moves (any play mode, any character).
Perfect Freeflow 2.0 (Bronze): Perform a perfect combo including all of Batman"s combat moves (any play mode).
Gadget Attack (Bronze): Use 5 different Quickfire gadgets in one fight (any play mode).
Perfect Knight - Day 2 (Gold): Complete every challenge in Arkham City - Main Story, Side Missions, Upgrades, Collectables, New Game Plus and Riddlers Revenge (as Batman).

The following trophies require the "Catwoman Bundle Pack" bonus downloadable content:

Arkham City Sirens (Silver): Drop in on an old friend.
Campaign Kitty (Bronze): Obtain all 108 medals on the original Arkham City campaigns (as Catwoman).
Family Jewels (Silver): Retrieve your stolen goods.
Feline Revenge (Bronze): Obtain all 72 medals on the original Arkham City ranked maps (as Catwoman).
Pick Pocket (Silver): Steal the score of a lifetime.
Sphinx" Riddle (Bronze): Complete all 40 of the Catwoman Riddler grid items.

The following trophies require the "Nightwing Bundle Pack" bonus downloadable content:

Campaign Nightwing (Bronze): Obtain 114 medals on the original Arkham City and Nightwing Bundle Pack campaigns (as Nightwing).
Nightwing Revenge (Bronze): Obtain 78 medals on the original Arkham City and Nightwing Bundle Pack ranked maps (as Nightwing).

The following trophies require the "Robin Bundle Pack" bonus downloadable content:

Campaign Wonder (Bronze): Obtain 114 medals on the original Arkham City and Robin Bundle Pack campaigns (as Robin).
Robin Revenge (Bronze): Obtain 78 medals on the original Arkham City and Robin Bundle Pack ranked maps (as Robin).