Rent a car and drive north on the highway that runs north/south down Italy’s spine. If you’re not in a hurry, you can visit Assisi, Perugia, Firenza, Siena, Vicenza and points north. in addition to the medieval cities, the countryside itself is beautiful. The further north one goes, it gets even better as you approach the Lake District.
Well, he said “cities”... otherwise I would also recommend the countryside sights in several places too.
It will cost you $300 a day to do a substantial drive in Italy with fuel and tolls. It is fantastic, but expensive.