Florence Side Trips for a day

Cinque Terre could be done. My first year I took the train to Riomaggior and then took the boat from town to town. When I got to Monterosso, had a late dinner and took the train back to Florence. As I remember, it was the last train and I missed my connection in Pisa (also the last train of the night). Two mistakes: should have eaten in Vernazza and never take the last train in Italy.

Assisi is about a 2 1/2 hour train ride. And it really deserves a couple of days!

Siena works and is spectacular. I suggest going/returning by bus. Nice scenery, convenient drop off near the medieval city.

More of a partial day trip, but I'm going to take the short bus ride to Fiesole when I'm in Florence on the My Way tour. Great views overlooking Florence.

What time of year? The Cinque Terre will be a zoo in the summer, a little less so in shoulder season. I wouldn't bother going in the summer, personally. Then again, I guess Italy will be busy almost everywhere in the summer.

I love the riviera and the Cinque Terre, but the biggest reason to visit in my view is to hike between towns. I don't think it's worth the time to go just to see a few of these small towns. There isn't much to see in them. I wouldn't go unless you plan to do at least one hike - and the trails that are now open are the 2-3 hour hikes (moderate hiking - not easy not especially difficult but a lot of steps up and down) between Corniglia, Vernazza, and Monterosso.

I loved Siena too. Obviously that's a different experience than the riviera towns - so up to you what you prefer.

I enjoyed my (local bus) visit to Fiesole that Eric mentions, but it's much less of a commitment time-wise than your other options.

You might enjoy one of these.

https://www.getyourguide.com/tuscany-l558/day-trips-tc172/

After you click on each tour, scroll down and read the full description.

The 6.5 hour Chianti or the 12 hr Montalcino,Pienza,Montepulciano
Would probably give you the best scenery and classic hill towns.

Recommend Siena, we did it a week ago as Florence day trip, took bus from Florence bus station just right of Florence train station with your back to trains, about 15 euros round trip per person. Buses run a couple of times an hour, trip is a little over an hour, maybe more at commute hour, try for a "Rapido" which avoids some stops in between. Siena cathedral is spectacular and just walking the town was different from Florence, because of Siena's hills and views.

Thank you for your replies so far!

Have you considered renting a car? We rented a car for one day in Florence and drove the back roads through Tuscany. It was probably my favorite day. With easy step by step directions from the GPS, we went to Certaldo, San Gimignano, and then to Sienna. We were able to stop at every curve in the road and soak in the vineyards and olive groves. It was a perfect way to experience the hill towns of Tusacany. We then took the interstate back to Florence after dinner in Sienna. I wouldn't try to do more than 3 towns this way, but there are certainly other itinerary options for a day's drive.