|Marble Garden Zone does exist, and it can be found in real encyclopedias. You may read more about it here:|
Marble Garden Zone makes a third appearance in Sonic Heroes 2. It is 'on top' of the Mystic Ruins underpass and is based moreso on its Sonic 3 carnation than its Sonic 1 carnation.
Team Rose play Marble Garden en route to Team Archaic in Station Square, as Amy has just got to see Sonic, and Vanilla is jealous and wants to see Mach. Team Underground play it en route to Gimmick Mountain Zone after Team Rose reports the wreckage caused by the Egg-O-Matic smashing into Gimmick Mountain. Team Big play it en route Mystic Ruins South. Team Chaotix visits the zone under instruction from Fiona Fox, who regards the fruit dropping from the trees a menace and wants them to pick it up. Team Covert plays the zone at night en route to Labyrinth Zone. Team Dark play it en route Jungle Zone and later Rouge and Fang play it again en route to Casinopolis. Team Babylon play it twice, once en route to Metropolis and once en route to, er, Metropolis (they wanted to go via Mystic Ruins train station but discovered once there that they couldn't as it was blocked). Team Badnik play it en route to Launch Base Zone. Team Eggman play it en route to Great Turquoise Zone, as they want the area's Chaos Emerald.