All of these are located in the Cell Blocks zone.
#1/#2: Next to the main entrance on the inside, immediately after the Electrical wiring clue. This room is to the left of the control room with spikes.
#3: On the upper level of the room to the right of the control room with spikes.
#4/#5: In the far upper right of the large room with the service elevator.
#6/#7: Immediately after exiting Cell Block C, and entering Cell Block B (on the way to get the Batclaw).
#8/#9/#10: In Cell Block B, in the room just before acquiring the Batclaw.
#11/#12: At the top of Cell Block C, after pulling down the wooden panel with the Batclaw. In the cells in the background.
#13: Above and to the left of Cell Block C, in an attic-like room where you have to pull down a wooden beam from the ceiling to break open the floor.
#14: Just below the wooden floor you broke in the room with #13. You can only get this one after the Bronze Tiger fight, so loop back here after it to get this cage (following the linear clockwise path on the map).
#15/#16/#17: Shortly after defeating Bronze Tiger, while following Penguin's blood trail, just past the electrified water.
#18/#19: In Cell Block D, in the foreground, on the bottom right, go through the door and go up one level to find these.
#20: In the hallway after Cell Block D, just before reaching the munitions depot to get Glue Gel.