Four hours are enough to go beyond the Ring. The first half of the ride covers the Vienna everyone comes for: the Hofburg, the cathedral, the Opera, the Parliament and the City Hall, the Belvedere and Schönbrunn. The second half goes where visitors on foot rarely reach: up to the Kahlenberg for the view, across the Danube to the tower, and back through the Prater.
Ten stops are a menu rather than a schedule. Choose the ones you want time at, agree them with the driver at the start, and see the others from the car. The ride is door to door, from your hotel or address and back to it.