What car was that?

I love films like these - especially where cars are involved. Can anyone tell me what kind of car was used as the taxi? (This is the scene early in the movie when Gina Lollabrigida says goodbye to Ronald Howard & his sisters at Piazza Navona and hops into the taxi) It's a cute yellow and green microcar, kinda like a conversion van that has been zapped and shrunk to one-third of its scale.