SPEEPSHighway | Sonic Adventure - Hidden Details and Secrets @SPEEPSHighway | Uploaded 8 years ago | Updated 7 hours ago
There's a lot of things in Sonic Adventure that are really easy to miss.
Here's a list I put together of some of the stuff I know.

I know a few things in there are rather common knowledge (such as teh Sonic statue), but I think everything has something interesting to point out.