Arkham Knight’s HQ is located inside the building that used to be the Killinger Departmental Store and you will gain access to it during the main story of Batman: Arkham Knight. It is located in the Drescher district on Founders’ Island and you can return to collect the 21 Riddler trophies here at any point in the story after that. Note that you must enter from the elevator at the top of the building.
Where to find all Riddler Trophies in Arkham Knight HQ?
Riddler Trophy #1
In the middle of Level 2, you will come across an alcove full of monitors across the entrance. Once inside, you will have to hit the question marks shown on the monitors with a Remote Electrical Charge to unlock the collectible.
Riddler Trophy #2
This collectible is located inside the AK HQ building. Head to the upper floor and look along the sides of the south end to find a sealed-up storefront. Hack your way inside and disable the turrets using the Riddler Bot to acquire the collectible.
Riddler Trophy #3
This collectible is located inside the Arkham Knight HQ building. Once you head inside, make your way to the left side of the area. Once you reach the upper level, use the REC Gun on the puzzle box and rotate it to find the collectible.
Riddler Trophy #4
This collectible is located inside the AK HQ building. You need to walk to the main platform and head inside the floor grate at the very top, crawl into a tunnel area, and you will find the collectible attached to a cliff across from you.
Riddler Trophy #5
You need to head to the opposite side of Level 5 and find an alcove with a turret placed in a corner. Blind the turret and stand on the pad to open up a grate followed by using a Batarang to hit a switch.
Disable the turret again, throw another Batarang to find the electrical charge, and hit the switch near the turret to claim the collectible.
Riddler Trophy #6
This is located in the Ventilation Shaft on Level 3. You need to park the Batmobile on the Pressure Pad and guide three Riddler Balls to the bottom of exits three times by shooting the corresponding question marks on the panel to acquire the collectible.
Riddler Trophy #7
You need to head over to the top of Level 5 and the bottom of Level 4 and find an alcove with Arkham Knight banners. Make the elevator go up using the REC Gun and drop down to claim the collectible.
Riddler Trophy #8
This collectible is located inside the AK HQ building. You need to head to the east side to a shuttered storefront. Hack your way in and guide two separate charges while continuously moving pipes in the correct areas to claim the collectible.
Riddler Trophy #9
This collectible is located inside the AK HQ building. You need to head to the east side of a shuttered storefront and find the collectible on a side of the base along the far wall, on top of a counter.
Riddler Trophy #10
This collectible is located inside the AK HQ building. Once you head inside, make your way to the left side of the area. Once you reach the upper level, you will see the collectible along a wall near the very end of the area.
Riddler Trophy #11
This Riddler trophy in Batman: Arkham Knight is located inside the AK HQ building. You need to head to the north hall of the base and head inside the last room to solve a puzzle and claim the collectible.
This is a simple puzzle where you need to pair up the identical images on the switches in front of you. What’s more, is that if you make a mistake, you don’t lose progress.
Riddler Trophy #12
There is a puzzle block located on top of Level 4 and bottom of Level 3. You need to make the ball drop down to the bottom using the Remote hacking Device to start or stop the rotating wheels and the switch on the panel to select the direction of the rotation.
Riddler Trophy #13
Head over to the bottom of Level 4, reach the Maintenance Sector, and find an alcove with Arkham Knight banners. Instead of heading towards the elevator, travel to a dead end and find a vent there. You will need to use the REC Gun to move the ball through the maze and claim the collectible.
Riddler Trophy #14
After you enter the large shaft in the HQ, grapple to Level 1 and you will find the collectible sitting on a desk there.
Riddler Trophy #15
You need to head to the bottom floor and find an area with a turret and an open elevator shaft. Head inside the shaft and grapple on the overhead floor. Once you are up, hack the terminal next to an elevator door and acquire the Riddler trophy using the Batclaw.
Riddler Trophy #16
This collectible is located inside the AK HQ building. Head to the north hall of the base and head inside the last room to find the collectible under a long table in the room with Asian decor.
Riddler Trophy #17
Grapple up to the top of Level 1 and find a control panel near a locked door. You need to use ‘Semiconductors’ as the password and head inside.
Complete the puzzle inside using the REC gun to initiate a charge and hit the question mark button to rearrange the pipes. Lead the charge to the very end to claim the Riddler Trophy in Arkham Knight HQ.
Riddler Trophy #18
This collectible is located on the bottom floor of the AK HQ. You need to head inside the large room where the Militia meeting took place and find the collectible in plain sight.
Riddler Trophy #19
Head over to the top of Level 5 and bottom of Level 4 and find an alcove with Arkham Knight banners. Take the elevator up using the REC Gun and use the Explosive Gel to claim the collectible.
Riddler Trophy #20
This collectible is located inside the AK HQ building. You need to move to the southern side of the base and walk down the escalators to find the collectible under the ceiling. Snag it using the Batclaw.
Riddler Trophy #21
Now make your way to the Briefing Room north of Level 5 and look for the Bar Lounge with purple neon lights. The trophy is sitting on top of the said sign and can be snagged using the Batclaw.
