I have every collectible in the game except for the 40th rat idol. I cannot find the final one to save my life! It is in between the Death Row and Gardens set in the menu.
On the map it appears on a section of map that overlaps with the rocky area you can glide between to get back to the batcave, but anytime I have tried to go there for it there is nothing but the rocky section.
Can anyone help me out?
#39/40 Rat Idols...
topaz wave
hexed swallow