Just got back from a 10 day trip to Italy. We did the classic Rome - Florence - Venice itinerary with Cinque Terre added in.
3 days in Rome. 2 days in Cinque Terre (staying in Riomaggiore). 3 days in Florence (including day trip to Pienza + Siena). 2 days in Venice (including Burano + Murano).
Italy was amazing as expected but unfortunately we went smack middle of the heat wave with high temperatures ranged between 90 - 100F. We were able to survive it by avoiding being out in direct sunlight during the middle of the day as much as possible (mini UV umbrella was a lifesaver) and drinking lots and lots of water.
Cinque Terre was a much needed break between Rome and Florence. Gave us the time to take things slow and rest our legs for a couple days. I highly recommend staying in one of the 5 towns. They have a lot of charm and are much more enjoyable after the day crowd disperses.
The day trip from Florence is the one part I would've done differently. We rented a car to drive to Pienza and while it was a lovely town, ultimately it was pretty small and not worth the long drive. Probably made more sense if we stayed out in the Tuscany countryside for a few days. We would've had an easier day if we had just taken the train to Siena instead.
Photos:
1-3: Rome
4-5: Vatican City
6-8: Cinque Terre
9-10: Florence
11-12: Siena
13-15: Venice
16-17: Burano