Where would you spend a month?

Florence because not only the city itself, but where you can go from there

Padova. Interesting and agreeable city without crowds. And so much within easy reach, from Bolzano and the mountains to Bologna and all the interesting cities in between, Venice at your doorstep, and even Trieste not too far away.

Someone else asked a similar question about Italy a few months ago, and I haven't changed my mind: I would not choose to spend the entire month in one place, because it would lead to a lot of back-and-forth on trains. I'd much prefer 3 or 4 bases during that amount of time because there is still much of Italy that I haven't seen.

Do keep the season in mind. At some point in October (possibly early in the month) the weather is likely to break, becoming cooler and wetter. For the second half of October I'd like to be in the south, I think. If you're prepared to rent a car, Puglia might be nice, but the smallest of the coastal cities--the ones depending on beach traffic to fill their hotels--might be sort of dead by then. In any case, I wouldn't choose to spend a solid month in Puglia at this point in my travel life.

A month on Sicily would be heaven, but you can't see the entire island from one base.

If I had a month, I'd split it between Florence and Rome. They are very different cities, and both have a variety of enjoyable day trips to offer. I'd be happy with either one for a month but if you haven't yet been to Italy, I'd split your weeks.

But what sorts of things are you interested in learning about? That can make a difference as the Rome area is heavy on antiquities, and Florence and surrounds leans to Renaissance/Medieval.

Venice, and try to take a month of intense Italian Language study. An Italian Language professor friend of mine said "But you're gonna end up with a Venetian accent!"

Roma. Or Roma and Firenze, as Kathy suggested.

Rome! The city has so much beyond the major tourist attractions. And it's central. Years ago I stayed in Rome for some weeks doing an immersion Italian program and it was such an​enriching experience on many levels.

If I were spending a month in Rome I think I would book lodging a bit farther from tourist central: perhaps in the Parioli area: fairly close in (just north of Villa Borghese) but green. Or maybe Prati? (I've stayed in the former but not the latter.)

I have to agree with Jim.
So much of Tuscany, Veneto and Umbria within a day trip by train, bus and car.

Thanks for all the good ideas! This is perhaps our 10th trip to Italy; we are looking forward to a relaxing trip without a lot of plans, just exploring at whatever pace we feel like. We tend to gravitate towards the Umbrian/Tuscan area, but have spent time in Venice, Florence, Cinque Terre, Positano, Matera and of course, Rome. It's fun to hear all of your suggestions. We usually travel in October/November but hadn't thought of planning according to the weather! Again, thanks everyone!