- You may be looking for the Green Hill Zone (Another Time, Another Place).
In the versions of reality reset by the first two Genesis Wave's, the Green Hill Zone was instead a territory on Mobius itself.
When the young Knothole Freedom Fighters each fell through a portal leading to different pocket zones, Sonic found himself in the Green Hill Zone, which was still in the process of forming. As he sped through, he eventually found Dr. Robotnik, whom wondered how he'd got into the zone, before attempting to do away with the young hedgehog with a wrecking ball attatched to his Egg Mobile. Testing out his Spin Dash for the first time, Sonic destroyed the Doctor's machine, before escaping back to the Prime Zone through a portal. (SSS: #9)
After Dr. Eggman initiated Operation: Clean Sweep, Sonic the Hedgehog found himself running in Green Hill Zone investigating the disappearance of animals. Here he encounterd the Badniks Motobug and Newtron, the latter of which took him to its leader, Snively, who was gathering animals in capsules. Sonic defeated Snively and destroyed the capsules, freeing Sally, Antoine, and Boomer from within one of them. Sally then lead the others to Marble Zone as part of a shortcut to Dr. Eggman's lair. (StH: #226)
Much later, after the Genesis Wave was initiated in a plan by Dr. Eggman and Dr. Wily to take over their worlds, Sonic once again found himself in the zone, this time searching for Tails, Amy and Knuckles who had mysteriously vanished, all the while, feeling an odd sense of deja vu. After Silver arrived to tell him of a disturbance in space and time that he'd traced back to this time period, Sonic came to the likely assumption that Eggman had something to do with what was happening, moments before being attacked by Copy Robot. Not too far away, Mega Man had arrived from his own world via Warp Ring, chasing after Metal Sonic. Once the two heroes where lured to the same location, a case of mistaken identity between the two of them led to a fierce battle, all of which where being broadcast to the Doctors by Tails Man. Before Sonic could win the battle due to his homefield advantage, Mega Man was able to retreat to his world through a warp ring opened by his father Dr. Light, as Sonic gave chase after him. (SU: #51, MM: 24, StH: #248)
- Green Hill Zone is the iconic first stage of the original Sonic the Hedgehog on the Sega Genesis, with variations appearing in later games. This makes it, by extension, the first ever stage of the entire Sonic franchise.