Sonic and Tails come across Robotnik's new base.
The Rusty Ruin Zone is an area of Flickies' Island, named for its ancient architecture. In Sonic 3D, the Zone is a vast area of rain-drenched crumbling buildings inhabited solely by mice and Flickies-turned-Badniks. In Sonic the Comic however, the Zone was reduced to a single massive ancient building, with a large amount of space below the surface. Its original builders and residents remain unknown, though the Drakons cannot be ruled out, given the presence of the Mobius Ring.
The Zone was primarily used as the third base of Doctor Robotnik, set up after the fall of his empire so he could investigate the Flickies' origins and use them as organic batteries for his new army of Badniks.After coming into contact with the Drakon Empire, Robotnik would continue to use the Rusty Ruin Zone as a base, launching armies of Badniks from there until he became a God with the power of the Chaos Emeralds.