2023 in Italy

If you are relying on train, bus or car, Florence provides faster options to other cities in Italy.

with 3-4 weeks, I'd use both. Always best to fly into Venice - spend several nights there.

Then take a train to Florence which deserves lots of time on it's own - plus, it's a great base for day trips into Tuscany. We used a company called WalkAboutFlorence for 2 day trips - check out their website - we loved their Best of Tuscany Tour and their Chianti Wine & Food Safari Tour.

Walks of Italy also does great tours in Venice, Florence, and Rome.

I'd end my time by taking a train to Rome as it's easy to fly home from. It's always best to fly into Venice and out of Rome.

You really have time to add Sorrento if you want - which is a great base for Amalfi Coast and Herculaneum. Then you could either fly home from Naples or Rome.

How about getting off the mass tourism track and base yourself in a place like Bologna, if you want a bigger ciity, or Orvieto or Perugia? You'll be in places with more Italians and have a more genuine experience.

Do you plan on visiting specific sites in Venice or Florence? If yes for me it would qualify for a few nights in one of the locations.

I highly recommend moving on to a less touristy based place as already suggested.

Will you spend more time in Tuscany/Umbria.
If so think about renting a villa as a base for day trips and allows down time to absorb more of the culture. Think like shopping at local market, talking to the vendors and creating a fun dining experience for yourselves.

You have a lot of time there so if you have an idea of things you like to do and see it would help you.

With your time frame of 3 -4 weeks, you have many options!
I find day trips a bit exhausting, so I prefer to spend 3-5 nights in several different places instead.

Some years back I spent 4 weeks in Italy and this was my itinerary:
Flew to Milan > Alibus from MXP to Lake Maggiore where I stayed in Baveno (separate day trips to Cannobio, and Lake Orta) >> train to Lucca (day trip to Pistoia) >> train to Siena >> train to Orvieto ( day trip to Bolsena) >> train to Assisi (day trip to Spello) >> train/ bus to Montefalco >> train/ bus to Trevi (day trip to Spoleto) >> train to Rome >> home.

What are your interests?

Do you have some good guidebooks?

When are you planning to go on your trip?

Happy planning!

Edited to add:
After replying to your post, I decided to start a new post which you might find helpful. Here’s the link: Remembering Zoe…Again.

Gosh, with 3-4 weeks to work with, I'd split the time between both cities, That will expand the amount of day trips that would be available to you within a reasonable amount of transport time (train or, in some cases, bus or water bus).

For instance, some from Venice:
Assorted islands (Burano, Murano, Torcello, San Michelle, etc. by vaporetti
Verona - approx. 75 - 90 minutes by rail
Padua (Padova) - approx. 30 minutes by rail
Bassano del Grappa - approx. 74 minutes by rail
Vicenza - approx 45 minutes by rail
Treviso - approx. 30 minutes by rail
Ferrara - between 70 minutes and 90 minutes by rail

Some from Florence:
Lucca - approx. 80 minutes by rail
Pisa - approx. 60 - 75 minutes by rail
Siena - approx. 90 minutes by rail or 75 minutes by Rapida bus
Rome - approx. 90 minutes by rail
Arezzo - approx. 70 - 80 minutes via rail
Fiesole - approx. 20 minute by local bus
Bologna - approx 40 minutes by rail.
Pistoia - approx. 30 minutes by rail
La Spezia, gateway to the Cinque Terre - approx. 1 hr, 45 minutes by 7:54 AM train from Firenze Campo di Marte station. This is a very specific train that only makes that run to La Spezia once a day. The same will apply to a return to Florence (19:48 train from La Spezia). From La Spezia, you'd take local trains to the 5 Lands villages, only a few minutes apart. I don't necessarily recommend this day trip, especially during high season, but people do it.

I'm sure other posters will have additional day-trip ideas! And yes, there's a great deal to be seen within Florence itself that you may have missed last time.