I'm guessing Comerica Park. A couple Warped Tours were there. Or how about Hart Plaza where the Detroit Electronic Music Fest and the Downtown Hoedown are?
Incidentally, I just landed back home in the dirty D for the holidays.
10/3 - Prosanctus Inferi / Horrendous ?
10/21 - Pallbearer / Tombs / Vattnet Viskar