My understanding of the question, the first post of the thread, is not whether it's ever actually been a race course, but if the facility depicted in the game is an actual place. To me, the R246, Seattle, and Rome courses are "REAL" as they've been mapped by me and others in this thread. They've never been raced on, like Long Beach for Champ Cars (and F1 in the glory days), but the streets are all actual places, the actual real-world scenery is depicted accurately in the game. Any of us with the desire, time, and resources to do so could pack up and go there, and see the places in real life. I don't know a better definition of a real place than being able to walk on it. . . . Saying Cote d'Azur is real and Seattle is not doesn't make sense to me. True the Seattle "course" does not exist as a racing event site, but the facilities depicted do exist. I think that was the original question, more than 2 years ago now(!!)
As far as we've determined, it seems that courses like Grand Valley, Apricot Hill, Deep Forest, Midfield, and Trial Mountain are fictitious places, and therefore not "REAL." They may have elements borrowed from real places, or even just inspired by real places, but as a whole, they are imaginary. OTOH, Laguna Seca is real. It has real races, and really exists. (As an aside, I wonder if it will be called just Laguna Seca in GT4, or will it be Mazda Raceway Laguna Seca?)
The jury still seems to be out on the Special Stage Route courses. Are they real places, or even based on real places? Everybody sees the ferris wheel in Route 11, but how many people see the roller coaster that surrounds it? Lots of people have said the bridge is the Rainbow Bridge, but the Rainbow Bridge is not a cable-stayed bridge like the one in the game.