|This location exists primarily or exclusively within the Pre-Super Genesis Wave continuity.|
Information in this article may not be canonical to the storyline of the games or any other Sonic continuity.
Hydro City is a location that appears in the Sonic the Hedgehog comic series and its spin-offs published by Archie Comics. It was an ancient and abandoned underground city filled with water located underground on Angel Island.
- Hydro City is based on Hydrocity Zone from Sonic the Hedgehog 3.
- Assuming Hydro City was built before Echidnaopolis, it would had to have been built under the ground and before the Angel Island was created.