Batman: Arkham Knight - 15 Hidden Easter Eggs, References & Secrets You Need To Find

7. The Flash

Like his arrow-flinging small screen compadré Green Arrow, The Flash's universe also appears to be tied to that of the Arkhamverse. Bust out the Batmobile, tear off around Gotham and you'll find a couple of posters for 'Hardwick Tours', taking intrepid Gothamites to other locations; one of which is The Flash's own city of Keystone. In addition, just to prove how much Rocksteady know the material, get down to the bowels of the GCPD building and you can find another image for Markovia; the land in which Batman travelled during the 80s to join up with little-known troupe, The Outsiders.