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.
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