There's this thing that games do that I love: when the game world reminds you of your accomplishments by putting them on display. I love how in Suikoden 2, I can build up my headquarters by recruiting companions and each time I bring a new person home, they take on jobs at my castle and help expand my home base. Or, in Assassin's Creed 2, all the paintings I collect, armor I discover, and weapons I purchase get displayed in my villa. I can see it all right there in the game world, and I get this hoarder satisfaction in seeing my neatly organized collection grow as I wallow in my accomplishments, reminisce on what I've done, and pat myself on the back.
That's why Batman Arkham Knight's Gotham City Police Department lockup is the best thing ever. Right off the bat (ha), there's an evidence room displaying all of the gear and gadgets of Batman's defeated enemies from the previous games, including the Joker's toy gun, Black Mask's mask, Crock's broken shock collar, and the swords of Ra's Al Ghul (and it's RAYsh, not Raz). You can walk up to each of the displays and listen to Officer Cash taking note of each item. Some of the comments are hilarious, such as when Cash tells a story about how he and several other officers got in trouble for making ice cream with Mr. Freeze’s freeze ray.
As you progress through the story and complete side quests, the jail cells in the GCPD begin to fill up with criminals. And these aren't just random criminals, they are the street scum you beat up yourself. The very first loud-mouthed thug you arrest can be seen later berating you from behind bars. If you decide you've heard enough, you can grab him and bang his head on the steel cage to teach him a lesson. Come back to that same thug later and he won't be talking so much trash and will flinch if you threaten to reeducate him.
Why do I love this stuff so much? Because it makes the world more believable and connected. Looking in the cells at the GCPD actually makes me feel like I'm saving Gotham City because that guy that was beating up a firefighter in the street is now locked up in jail. I did that. I put him there. And now he's all pissed off at me. It's great. Also, the firefighter I saved from that severe beating is in the GCPD recovering and he regularly thanks me for saving his life. It's nice to feel appreciated, you know?
The cells also have labels for the criminals according to affiliation. So you can know that those Penguin gang thugs were there when I blew up that weapons cache that one time, or that the Two Face low-lives in the other cell tried to rob one of the Gotham banks two nights ago. Putting the affiliation on them makes the game feel more alive when I see those connections, and the faceless, bat fodder enemies aren't just throwaway goons I beat up and left for dead. (I can only assume they actually got picked up by the cops and received medical attention after I shattered their face bones into a million pieces.)
I love walking around the GCPD. I get the satisfaction of seeing my accomplishments right in front of me, there are fascinating Batman easter eggs all over the place, and the atmosphere of it makes me feel like I'm legitimately in the middle of a crisis. But best of all, thanks to the GCPD lockup, I know all those criminals I've put so much effort into fighting are right where they belong.