Prison Island (Sonic X)

Prison Island is a location that appears in the anime series Sonic X and its comic series published by Archie Comics. It a high security military base under the authority of GUN.

Anime
Prison Island is a considerably old military base, evident by the fact that Shadow was sealed within said base some 50 years ago.

Prison Island is first shown when Eggman is invading it upon discovering the research and works of his grandfather, Prof. Gerald. Eggman infiltrates the place, and releases Shadow, who then informs Eggman of the Eclipse Canon, saying that with the seven Chaos Emeralds, Eggman could use the cannon to rule the world.

The island is once again shown after Sonic is taken there by GUN. Tails, Amy, Chris, and Tanaka had arrived there to save Sonic. While there, Tails does battle with Eggman and Amy infiltrates the location, helping free Sonic from his prison. Dashing off into the nearby forests, Sonic then encounters and has a quick quarrel with Shadow, before learning of the fact that the island is about to blow up. Running away, Sonic manages to escape the island alongside the rest of his allies just as the island begins to be destroyed by Eggman's bombs.