In Panessa Studios, there's a room with generators that holds one of Riddler's riddle.
To get the riddle, the generators needed to be hit in a particular order. As far as I know, there weren't any hints to the order that should have been taken. Detective mode didn't reveal anything. I couldn't see any obvious hints in the posters. After a number of random guesses, I was eventually able to get it.
Starting from the left: 1 5 7 3 2 4 8 6
How was I supposed to know in what order to hit the generators?