Art by Stephen Davis
Turquoise Hill Zone is one of the many "Hill" Zones located on South Island. Turquoise Hill looks very much like Emerald Hill and Green Hill, with very little setting it apart from them.
This zone never appeared during STC's main run, but appeared in Sonic the Comic Online's 250th issue in The Battle For Mobius. The brief scene shows the Turquoise Hill Freedom Fighters - Tux, Joe Sushi, Tufftee, Flicky and Sally Acorn - defending the Zone from Doctor Ivo Robotnik's Badniks.
Turquoise Hill originally appeared in the Sega Game Gear game, Sonic Chaos.