Need advice on where to visit next

It's striking that you've not gotten any replies yet. Probably because there are way too many places in the enormous space of Europe that would work. I suggest going at it this way: when you read a book, watch TV or a movie, watch a Rick Steves show, etc, what place captures your attention? Go there.

Ditto KC!
Most cities in Europe are walkable. Lots of art and history everywhere.
Food and wine--What is great to you? What kinds of cuisines do you typically enjoy?
So, tell us something else about yourselves and your likes that would help us make suggestions.
I think just searching airfares is never a terrible way to go.
I'll throw out Lisbon and Porto, though I have not been yet and don't favor Portuguese cuisine.
Paris and Lyon would be nice companions.

Also add the month, as that can spark ideas too.

Are you stuck on Italy? Try another country, culture. There is so much out there. My suggestion is somewhere not Italy.

You could consider the German-French border--Heidelberg, Strasbourg, Colmar, Freiburg/Black Forest. Great wine, beautiful cities that are walkable, and beautiful villages and countryside around those.

I don't know if that's to broad and you wanted more of a single-city rec, but maybe this gets you started?

London and Paris

Vienna and Budapest

Prague and Berlin
Pick two in Spain
Rome and Naples
Istanbul and Antalya
Lviv and Krakow

Thanks to all who replied, I really appreciate it!
We're definitely set on going somewhere other than Italy (but will visit again soon!), there are some great rec's for us to consider.
Thanks again!

Prague/Budapest/Vienna

Basically, if you loved Bologna and Florence, you'll really love___________.

Bordeaux and Lyon.

Spain! Great food and wine, beautiful historical sites, and lots of gorgeous beaches if that's your thing. Northern Spain- Barcelona with day/overnight trips to Girona and Figueres for the Dali museum. Southern Spain- Granada and Seville and possibly Cordoba too.

England- London and York
well, I don't think it is very close to Italy.

For Italy, I recommend Siena, Lucca and in the Naples area Sorrento, Capri, Amalfi Coast and Pompeii.

Hi there, and welcome to the Forum! When were you thinking about traveling? Sounds like you had a fantastic time in Italy & great you chose some smaller places. The thing that strikes me about if you loved Bologna and Florence, you'll really love____ is that these are 2 very walkable, smaller cities, rick in culture where basically everywhere in the center has extraordinary sites. In which case, I would continue to look at smaller cities - I think Howlinmad & Threadwear's suggestions are the closest to what you found in Northern Italy. And I agree, 2 cities is probably enough. Emyee's idea of Southern Spain also works if you go in the off season. Here's an example - https://www.ricksteves.com/watch-read-listen/read/articles/the-allure-of-cordoba

A great place to start is at the library. After literally 50 years of traveling & at times living in Europe, I still go grab a stack of books to research new places. And take a look at RS's videos here on his website, he's done great ones on all the countries. https://www.ricksteves.com/watch-read-listen/video/tv-show. Good luck!