Cognomix is an Italian web site which offers resources and services as an aid in learning more about Italian surnames.
One of the services is Mappe dei Cognomi Italiani (Map of Italian Surnames) which can be accessed from this link: http://www.cognomix.it/mappe-dei-cognomi-italiani/.
Enter the Cognome (Surname), select Dove (Where) and press Cerca! (Search) and you will be presented with a map of Italy showing the concentrations of the Surname across the selected search area.
Where to search options include all of Italia (Italy), a Regione (Region) or a Provincia (Province) within a Regione.
For example, searching for the surname CEFALO in Avellino reveals 48 Cefalo's in Avellino including 7 Cefalo's in Torre le Nocelle.