A day stop while traveling between Venice and Florence

You won't find it in the RS book, but Bologna is an easy stopping place, great food, sights, excellent train connections.

Padova and Bologna are the 2 big stops along the route, and both made by the high speed trains.
It's a tough choice. I'd go with Padova for the Scrovegni Chapel and St Anthony's Basilica.

Between Venice and Florence, the train passes through Padua, Ferrara, Bologna. All three are worth a visit, so I'll leave that to you. However Padua is very close to Venice (20 minutes) and you might consider a visit there for a few hours while you are in Venice.

The problem with making a "day stop" at any of those towns, is that you'll be hauling your luggage and will have to store it while you're sightseeing. You could also consider going directly to Florence and making day trips to any of the cities mentioned (or others such as Lucca or Siena).

I would suggest Bologna. Far enough that after a walk, you might be hungry and they have some excellent food there. Add to this what is widely considered the world's first university and sights such as the Due Torri (Two Towers), the Fountain of Neptune, the Piazza Maggiore, and the Basilica of San Petronio (15th largest in the world, has Cassini's meridian line or perhaps Giovanni da Modena's fresco with Mohammed being tortured in Hell would be of interest). You'll easily find something.

VERONA...easy walk from train station to B&B...Juliet's balcony, Roman theatre
and nice restaurants but a break between the crowds of Venice & Florence.

Verona has its spectacular Roman arena, venue for summer opera, as well as remains of a Roman theatre above the river.

Thanks everyone for the suggestions. Ken, you made a good point about luggage storage. Is this a big inconvenience and/or a safe venture?

not to beat a dead horse, but Juliet's balcony is not a site- It's a made up tourist attraction that has nothing to do with the ...oh, well, we should to stay away.

Verona is one of my favorite Italian towns. In fact, it does have a Roman theatre, but it is the least interesting sight in the city. The Arena is the best, but there are half a dozen others that are excellent.

Bologna Centrale has a left luggage office. Or at least it did earlier this year!

Ralph, I find it very appropriate that the Veronese made up a balcony to go with a fictional character. (^_^)

If you have read Frances Mayes' books, I'd suggest Verona.