Monaco

Located between France and Italy, this small city-state is truly a place for the rich. From the famous casino to the crowded marina, there is no place for small and cheap cars. You will rather see a high density of luxury cars.
Monaco is definitively worth a visit, and the casino (at least from outside), the marina and the palace are the highlights of this city-state. I also recommend to walk a bit apart from the tourist trail in smaller streets in order to get a better feeling of how life is in Monaco.
Keep in mind though that restaurants are on the expensive side. And Monaco is not part of the (free) EU roaming agreements for mobile phones.