row 1, Riddle 1
Subway Access - From the Industrial District entrance, head forward and over the first gap. Take a left and you'll come to another gap (which has a statue on the far end if you haven't collected it). Line launch across the gap. There is a destroyable section of ground here. Destroy it and drop through the hole. On the table in this room will be a giant collar with a chain. Scan this.
row 2, Riddle 1
Subway Tunnels - Enter from the Subway Terminal and then head up the southern tunnel a little bit. The last train car that you can walk on can also be entered. Walk through the car and you'll notice one of the windows is still intact. In fact, it's a mirror. Turn on Detective Mode and you should see a dot on the mirror and the reflection of a question mark on the wall behind you. Line up the dot so it makes a full question mark and then scan it.
row 3, Riddle 1
Subway Station - On the bottom floor of the station, in the northwest corner will be a Vicki Vale Show poster. Scan the poster.
row 4, Riddle 1
Subway Tunnels - By the exit leading to the Subway Terminal, you should find a Titan tank. To the left of the tank you should see a giant mural on the wall of Solomon Grundy. Scan this.
row 5, Riddle 1
Subway Terminal - From the door that exits the area to the north, follow the wall to the left. Just before the end of the wall should be a poster that says "Visit Santa Prisca." Scan this poster.