If you don't like the sight of parking garages, and the thought of how much fossil fuel oversized cars are consuming, then the old neighborhoods of Rome can come as a relief. Narrow streets and very limited parking has created what for an American is a parallel universe populated by scooters and tiny cars.
The "smart" car--a small car with an attitude that is coming to the States this year--is a common sight. It's so short it can park like a scooter if the space is too minute for parallel parking.
I had read that Rome's streets are noisy and dangerous, but in the old district, at least, there was a lot of gentle driving going on, and the reported racket of car horns turned out to be only a periodic, polite peep.
When I was ten years old, I visited Europe and, when I wasn't throwing rocks in alpine streams in an imaginative effort to re-sink the Bismark, I was admiring the scooters that quietly zipped people around. Decades later, I have the same reaction. Motorcycles without the macho connotations.
A web search suggests that the 'smart' cars don't get particularly spectacular gas mileage--in the 30 to 40 mpg range. Scooters are up around 85 mpg.