Batman: Arkham Asylum

This one's a hub of misinformation it seems! You need to scan all the "Chronicles of Arkham" to unlock this achievement.

I've taken the liberty to gather Chronicle locations using this excellent resource: http://www.gamesradar.com/f/batman-arkham-asylum-riddler-gui....

Locations are as follows:

ARKHAM EAST - CHRONICLE #1
Left of the Arkham Mansion stairs is a locked-off courtyard. Grapple over the wall, drop down and check the righthand wall - behind the railway - for a tablet.

ARKHAM EAST - CHRONICLE #2 (TOOL NEEDED: Explosive Gel)
Face the Botanical Garden staircase from the graveyard. You should notice a patch of destructible wall on the side of those stairs. Use your gel or your Ultra Batclaw to get inside and find the tablet.

ARKHAM WEST - CHRONICLE #1 (TOOL NEEDED: Explosive Gel)
Underneath the Penitentiary balcony is a destructible arch. You can spot it best while standing amidst the ambulances. Grapple up, explode the wall and scan the chronicle symbol.

ARKHAM NORTH - CHRONICLE #1
Find the crumbling building to the west of the main asylum gate. When going through the door, look up and right and you'll see an alcove. This is where the beetle symbol awaits.

ARKHAM MANSION - CHRONICLE #1 (TOOLS NEEDED: Batclaw, Explosive Gel)
(Mansion Entrance Hall) -You'll see this on your way from the Main Entrance Hall to the Main Hall. The door between them is locked at first, so you're forced to grapple into a ceiling air duct and crawl through. The tablet is halfway along that path, in a room right after a desctructible wall.

BOTANICAL GARDENS - CHRONICLE #1
(Abandoned Chamber) - Follow the same complicated path you did to get to Riddle #8. In fact, the exact spot where you stood to scan Riddle #8 is the exact spot you need to jump from to reach this chronicle. Make sure to get a slight running start, then leap towards the northern wall and catch hold of the ledge. Shimmy left and climb up to find the tablet.

BOTANICAL GARDENS - CHRONICLE #2
(Glasshouse Entrance) - When trying to exit the Botanical Gardens, Poison Ivy will block your way with huge, tentacle-like vines. Drop down through the floor and, before continuing with your mission, turn around and scan the beetle symbol behind you.

BOTANICAL GARDENS - CHRONICLE #3 (TOOLS NEEDED: Line Launcher, Ultra Batclaw)
(Titan Production Facility) - Remember when you used the Line Launcher for the first time, leaving the fight with Joker's two deformed henchmen and heading out to find Poison Ivy? You would have zipped across a gap to the exit. On either side of that exit, however, is a reward. On the right is a trophy. On the left is a destructible wall (you'll need to return with the Ultra Batclaw) and a Chronicle of Arkham.

CAVES - CHRONICLE #1
(Old Sewer) - Drop into the Old Sewer from the Batcave path and turn right. You should see the tablet only a few yards away from you, against the brick wall.

CAVES - CHRONICLE #2 (TOOL NEEDED: Ultra Batclaw)
(Pressure Control Junction) - In order to escape the Caves after shutting down the Titan pumps, you need to Ultra Batclaw a couple of walls down in the elevator shaft. Behind the first one, you'll find a message from Amadeus Arkham.

CAVES - CHRONICLE #3 (TOOL NEEDED: Ultra Batclaw)
(Control Room) - As you enter this area, you can turn left or right and see a destructible patch on either of the diagonal walls. The one on the right hides a chronicle tablet. Use the Ultra Batclaw to gain entry. (Having trouble re-entering the pump section later in the game? We did too! See our solution under Patient Interview #5.)

INTENSIVE TREATMENT - CHRONICLE #1
(Secure Transit) - You can't miss the beetle symbol as you're climbing the elevator shaft. It's near the very top, right before an encounter with enemies.

INTENSIVE TREATMENT - CHRONICLE #2 (TOOL NEEDED: Explosive Gel)
(Secure Transit) - You might also spot this tablet while climbing, if you have your Detective Mode turned on. About halfway up, through a crawl space, there's an empty room with two destructible walls. The chronicle's behind the left one... return when you have the explosive gel (or Ultra Batclaw).

INTENSIVE TREATMENT - CHRONICLE #3 (TOOL NEEDED: Ultra Batclaw)
(Transfer Loop) - In the eastern roundabout area of the Transfer Loop, keep your eyes toward the ceiling until you spot a high wall grate. Grapple to the opposite air duct, use your Ultra Batclaw to pull down the grate and carefully jump across to grab onto the small ledge. Once inside the secret area, you'll find the tablet with no problem.

MEDICAL FACILITY - CHRONICLE #1 (TOOL NEEDED: Explosive Gel)
(Sanatorium) - When you enter the Sanatorium from the Medical Foyer, turn left and walk along the western side of the room. Tucked between the first and third patient rooms is an empty area with a destructible floor. Blast it and drop down to find the chronicle.

MEDICAL FACILITY - CHRONICLE #2 (TOOL NEEDED: Ultra Batclaw)
(Medical Foyer) - Go to the Sanatorium door, but rather than exit the Foyer, turn 180 degrees and check the wall opposite. It's destructible if you have the Ultra Batclaw and the beetle tablet is behind it.

MEDICAL FACILITY - CHRONICLE #3 (TOOL NEEDED: Ultra Batclaw)
(X-Ray Room) - This is where you first met Dr. Young, rescuing her from thugs. Grapple to the roof of the X-Ray area - which also holds a trophy - and turn back towards the exit. You should see a destructible panel on the wall. Pull it down with the Ultra Batclaw and jump in to scan the tablet.

PENITENTIARY - CHRONICLE #1 (TOOLS NEEDED: Cryptographic Sequencer, Explosive Gel)
(Extreme Incarceration) - In the room where you lock up Harley, check out cell #5 on the upper right side. Inside is a trophy... and beyond that, an Arkham chronicle. To get inside, you'll need to head back to the main control tower and go upstairs to the numbered security panels. Use your sequencer to hack into panel #5 and the door below will open. Nab the trophy, then destroy the cell's back wall with gel. The chronicle symbol is revealed! To escape afterwards, just grapple up.

PENITENTIARY - CHRONICLE #2 (TOOL NEEDED: Ultra Batclaw)
(Guard Room) - To gain access to this chronicle, you'll need to get rid of the Joker toxin in the Guard Room first. See the Prometheus Riddle for how to do so. Once the area's cleared, check the southern wall for a destructible panel, and beyond it, the beetle symbol.

PENITENTIARY - CHRONICLE #3 (TOOLS NEEDED: Explosive Gel, Line Launcher)
(Main Cell Block) - In the short hall that leads from the Main Cell Block to The Green Mile, watch the left wall for a destructible patch. Beyond is a long stretch of electrified water. To get across and scan the chronicle, you'll need the Line Launcher.

Then, as "All Time Best" and "Batman5273" said, go get that last scan. Voila!

After solving all of the riddler challenges, head back to the penitentiary and go to the room where you rescued the warden. There is a circle on the floor with the word BATMAN written in the center. Investigate it to unlock this achievement.

Here is a great guide for ALL collectibles
http://guides.gamepressure.com/batmanarkhamasylum/

I found with a great map and photos of the area. In my case, I missed some of the Cave and Croc Lair ones, so it is handy to have a quick look at the general area.

Here is a Video Guide for those who don't want to read and want a visual aid. It's also quite convenient!

Enjoy and thanks for watching!

In short, get every Amadeus chronicles shown on the map (23), then go to -> Arkham West -> Penitentiary -> Security Control Room (south of the map) -> Look at the floor of the tower