A few years ago, my dad won an XBox as a door prize at some event and, for his next birthday, we got him Project Gotham Racing 2 (PGR2). I played it a fair bit too and absolutely loved it.
When I was in Florence at the end of last year, I confess I actually recognized some of the roads from PGR2. I went looking online to see if someone had mapped out all the courses on Google maps but couldn't find anything.
There are some screenshots on Flickr from Bizarre Creations showing the course models. For example at http://flickr.com/photos/bizarrecreations/304326348/ but nothing to really tie the course to the real place.
This evening I found http://www.moondookie.org/pgr2tracks.html which has 12 of the courses drawn over satellite images. It would be nice to have a more complete set, though, and in machine readable form.
Actually, what would be really nice is having the actual models (like the one depicted in the first link). I guess it's too much to hope for that :-) Google's 3D Warehouse is probably best bet of having something anywhere close.