A Zone on Mobius filled with ancient Roman-esque buildings and structures. Much of the ancient architecture has sunk into the enormous lake that makes up the Zone. Any structures left above water are all covered with overgrown greenery. A number of ancient booby traps are laid out across the Zone, many of which still work. The Zone is also afflicted by tremors on a regular basis, resulting in more of the ruins submerging. Because of these hazards, no one comes to the Aquatic Ruin Zone and even Robotnik mostly left it alone during his rule.
It was established in Sonic the Comic Issue 109 that the Aquatic Ruin Zone is in fact the site of a former Drakon colony, and that the Drakons were responsible for creating the giant Sentinel that Sonic once encountered there.