Both the Old Town and the New Town across the river are highly pedestrianized. A car is not only unnecessary in Girona, but also quite cumbersome. Rentals are available for those wishing to make day trips to the outlying villages and castles in the area.
It should be noted that most of the streets in the Old Town have large cobblestones and steep stairs going up the hill upon which Girona is built. Walking in high heels or with rolling luggage is quite difficult at some points, so plan accordingly.