Two nights in Tuscany between Florence and Rome

I would go to Siena, but bus is better for getting there from Florence and to Rome. Montepulciano does not lend itself to a public transport trip, and I don't think Cortona does but maybe someone will know if there is a good bus route, as there is for Siena.

I went to Arezzo for a couple of nights between Rome and Florence a few years ago and really liked it. It’s a nice walkable town with some hills. There’s the wonderful Basilico di San Francesco with amazing frescoes. The cathedral is also beautiful. The city was a good change of pace between the 2 much busier cities. Easy to get to by train.

Siena is my favorite city in Italy -- I'd certainly do that. Unfortunately most of the fabulous stops between FLorence and Rome are not easy to do without a car. We loved Montepulciano, Pienza, Saturnia and the hot springs waterfall in the park on the edge of town, the Etruscan tomb cities north of Rome Tarquinia and Cervetari and the Etruscan tombs in the hills above Sovana. Small towns don't have train stations.

Siena is easy as a day trip from Florence -- Siena to Rome by public transport is tricky and not direct.

We went round trip between Rome and Siena and it was direct and just fine. Flixbus. https://www.flixbus.com/bus-routes/bus-siena-rome

I think you will love Siena!

You don't mention art, but Siena has some of the most interesting paintings in all of Italy, such as the early 14th century Allegory of Good and Bad Government frescoes: https://en.wikipedia.org/wiki/The_Allegory_of_Good_and_Bad_Government

Also the mosaic floor of the cathedral and the frescoes in the Ospedale di Santa Maria della Scala. What I mean by "interesting" is that even people who normally don't enjoy art (especially religious art or early Renaissance art) will find much to look at and think about.

Thanks for the ideas. I think I’m going with Arezzo, as a friend in Firenze, whom I respect very much, recommended it. This holiday trip is designed to be low key and leisurely - my first night (Christmas) will be in Rome, then to Firenze for two nights, followed by Arezzo for two nights and finished in Rome with four nights. Already looking forward to it!

Given the time of year, when Siena may get plenty of visitors, that is probably a wise choice for a low-key experience--have a great tip!

If going to Arrezzo then be sure to reserve tickets for the Piero Dela Francesco frescoes. We did a day trip to Arrezzo from Florence about 20 years ago and could not see them as they were totally booked up. I imagine it is much much worse now as all tourist sights are tremendously overcrowded.

We spent two months in Florence 22 years ago and a week about 12 years ago -- and then two weeks last fall. We were shocked at how totally overwhelmed central florence is now with tourists. It has always been popular and crowded but it is exponentially more so. e.g. to get a Vivoli ice cream cone would involve at least a half hour line. There is no ice cream I am willing to spend that kind of time in line for. We used to drop by and wait 10 minutes tops.
Just walking across the Ponte Vecchio something we did every morning 22 years ago is now cheek by jowl and totally unpleasant.

We feel very lucky that our first travels to Italy were 40 years ago when we were the only tourists on the day we visited Volpeia and walked the Cinque Terre before Rick Steves publicized it. We were the only Americans we saw that day and the only other hikers we encountered were Italian middle school students and their teacher.