Computer and Video Games have posted a report of the "Behind closed Doors" demo of GT4:

    "Kazunori Yamauchi, head of Polyphony Digital's Gran Turismo team, confirmed that GT4 will feature 500 different cars, including standard models, convertibles, modified motors, souped-up racers and "historically significant" vehicles.

    As well as realistic environments from locations around the world including New York, Paris, London and the Grand Canyon, GT4 will also feature licensed circuits from every corner of the globe, including tracks from Japan, Europe and the United States, bringing the total number of courses to over 100."