South Island

South Island is an island featured in the Sonic the Hedgehog series, traditionally recurring in the earlier titles. According to Japanese manuals, it supposedly shifts along the water due to some connection to the Chaos Emeralds.

South Island first appeared in Sonic the Hedgehog for the Sega Mega Drive, and later appeared in Sonic the Hedgehog, Sonic the Hedgehog 2, and Sonic Chaos for the Master System and Game Gear. Its next appearance was in Sonic the Fighters, an arcade game. Following that, it was in Sonic Adventure 2, where a 3D rendition of the Green Hill Zone was a secret, unlockable level. After that, it appeared in Sonic Battle as Emerald Town. Its latest appearance was in Sonic Chronicles: The Dark Brotherhood, where Green Hill Zone was the first area in the game. Sonic Battle revealed that Central City was on the island, andSonic Chronicles: The Dark Brotherhood revealed it held the Mystic Ruins, as well.

Sonic the Hedgehog (16-bit)
In Sonic the Hedgehog, Sonic goes to the island and finds that the evil Doctor Robotnik built a base on the island and turned the local wildlife into robots. The heroic hedgehog stops Robotnik while collecting the Emeralds. Zones of the game are below:
 * Green Hill Zone, grassy plains with lakes and waterfalls. This zone has appeared in several other Sonic games as well. It is without a doubt the most iconic level in all of Sonic history.
 * Marble Zone, ancient ruins half-sunk in lava.
 * Spring Yard Zone, an urban area with pinball bumpers and springs.
 * Labyrinth Zone, an underwater maze.
 * Star Light Zone, a peaceful, highway-like city area at night.
 * Scrap Brain Zone, a heavily industrialized area which serves as Robotnik's base.

Sonic the Hedgehog (8-bit)
The story in the 8-bit Sonic the Hedgehog is the same as in the 16-bit one, and the games most likely depict the same adventure. Zones of the game are below:
 * Green Hill Zone, sporting the same verdant fields as in its other appearances.
 * Bridge Zone, a long bridge over a river.
 * Jungle Zone, a rain forest with wild rivers and vines.
 * Labyrinth Zone, the same submerged ruins as in the 16-bit game.
 * Scrap Brain Zone, the Doctor's industrial stronghold.
 * Sky Base Zone, a large, weaponized zeppelin made by Robotnik.

Sonic the Hedgehog 2 (8-bit)
In Sonic the Hedgehog 2, Dr. Robotnik returns and kidnaps all the inhabitants, along with Miles "Tails" Prower, demanding a ransom of six Chaos Emeralds to return them. Sonic goes out to stop him once again and succeeds. The Zones of the game are as follows:
 * Under Ground Zone, a volcanic mountain, once used as a mine.
 * Sky High Zone, the top of a mountain that reaches the clouds.
 * Aqua Lake Zone, a lake surrounded by fountains and pillars.
 * Green Hills Zone, very like the one from the previous games, but with normal trees instead of palm trees.
 * Gimmick Mountain Zone, one of Robotnik's metallic bases, apparently set inside a mountain.
 * Scrambled Egg Zone, a mountain filled with large pipes, and another of Robotnik's bases.
 * Crystal Egg Zone, a transparent crystal base of Robotnik's. Can only be accessed with six Chaos Emeralds.

Sonic Chaos
In Sonic Chaos, Robotnik steals one of the Chaos Emeralds on South Island and as a result, the rest of the Emeralds become unbalanced and cause the island to slowly sink into the ocean. However, Sonic recovers all the Emeralds and saves the island. Zones of the game are below:
 * Turquoise Hill Zone, a grassy hillside area, much like Green Hill Zone.
 * Gigalopolis Zone, a sprawling urban area with various passages. The Game Gear version spells it as "Gigapolis Zone".
 * Sleeping Egg Zone, a mostly flat region of plains, with Eggman's self-portrait adorning parts of the background.
 * Mecha Green Hill Zone, Robotnik's version of the Green Hill Zone, with deathtraps strewn everywhere.
 * Aqua Planet Zone, a group of ruins partially submerged in water. Despite the name, there is actually very little water.
 * Electric Egg Zone, another of Robotnik's many large bases.

Sonic the Fighters
In Sonic the Fighters, South Island is one of the battle arenas. It is the very first arena in story mode, and is where the player character faces Knuckles the Echidna. The arena is set on a small island plateau, in an area that looks mostly like the Green Hill Zone. If the player plays as Knuckles here, the player will fight a shadow Knuckles.

Sonic Blast
In Sonic Blast, Robotnik's latest floating base threatens Sonic's home, so Sonic and Knuckles resolve to take it down. While the location was not specified as South Island in the western storyline, the presence of another version of Green Hill Zone further implies it, and the Japanese instruction manual confirms it. Zones of the game are below:
 * Green Hill Zone, a version of the series landmark.
 * Yellow Desert Zone, a large yellow desert with Egyptian caverns.
 * Red Volcano Zone, an active underground area surrounded by molten rock.
 * Blue Marine Zone, the waters off the coast inhabited by ancient ruins.
 * Silver Castle Zone, Robotnik's massive station that rose from the ocean.

Sonic Adventure 2
In Sonic Adventure 2 and its GameCube re-release, Sonic Adventure 2: Battle, Green Hill Zone was a secret stage that could be unlocked by obtaining all 180 Emblems. On the Stage Select screen, the icon for Green Hill could be found on a secluded island, presumably South Island.

Sonic Battle
Sonic Battle features Green Hill as an unlockable arena unrelated to Story Mode. In addition, as Central City would later be shown to be located on South Island, it introduces Emerald Town, Holy Summit and Night Babylon as neighboring areas on the island.

Sonic Chronicles: Dark Brotherhood
South Island appears here as the western landmass in the first part of the game. In addition to Green Hill Zone and Central City, it reveals that the Mystic Ruins and the remains of Station Squareare also found here.

Sonic Generations

 * Main article: Green Hill (Sonic Generations)

Although South Island itself is not mentioned in Sonic Generations, one of its main locations, Green Hill, makes its reappearance as the first level in this game.

Sonic the Comic
In the fortnightly publication Sonic the Comic, South Island is the setting of many stories. Sonic the Comic #25 reveals that South Island is the location of the many "Hill Zones", including not only the Green Hill Zone but the Emerald Hill Zone as well (which, in the games, is located on Westside Island). On the northern part of the island is the Frozen Zone, which contains the North Cave, where Sonic the Hedgehog once hid the Chaos Emeralds.

Sonic the Hedgehog: The Movie
South Island appears in Sonic the Hedgehog: The Movie as part of the Land of the Sky on Planet Freedom and, is ruled by the President. It is also the area where the movie begins.