Yes it is indeed Detroit. It might not be a circuit normally associated with water but the start/finish section ran right next to the Detroit river. So well done you get the final point in this puzzle.
I was thinking of doing a second puzzle of this type. I knocked this one together pretty quickly so I would spend longer on the next one and make it (hopefully) much harder with more obscure/less eaisly reconisable circuits. Then I'd probably open it up to everyone straight away by putting it into the pros section (since they didn't get a chance with this one).
So what do people think about these kind of big multi answer puzzles? Would people be up for another, better, harder sequel to this puzzle? Let me know what you think.