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!

Thanks all, appreciate all the suggestions!

San Sebastian and Bilbao

Ferrara, Visby and Crete.

Paris and Normandy towns
Paris and Lyon
Paris and Alsace towns
Paris and Bordeaux
Paris and Nice

Agree with CJ....
Paris and Normandy
Paris and Provance region.
Paris and Strasbourg

London and York
London and Canterbury area

Vienna and Salzburg

You didn’t say when? That does change things. So I will assume March thru October.

Lots of choices as the list above illustrates. All are good. But I only talk about what I know and that’s obviously not for everyone.

Sounds as though you like city destinations. If at least half the trip could be more rural I would suggest Montenegro (list of video links here: https://community.ricksteves.com/travel-forum/montenegro/podgorica-to-dubrovnik-by-car). But if the majority is city, then, among the others listed above, Budapest

Walkability: Walking alone, maybe an 8. But the surface trams are great tour busses and they open a way to reach other locations within the city to explore on foot. So if you throw that in I give it a 10.
https://youtu.be/14e80xGLxSI?si=8Ebu_PCWqZPG4fgz
https://youtu.be/nOAlQxuQZWE?si=HkVbFwYPvQntijId
https://youtu.be/SLQffU693a8?si=EqP-AGDH_f_G5YDs

Great food: Lots of places can boast good food and wine, Budapest has a remarkable food scene as well. From Michelin star to purely home cooking in a local setting. And as you would expect from a large city there are restaurants representing every corner of the world. Hey, you don’t go to Chicago and only eat pizza. You go for the world and world class dining.
https://youtu.be/QborfsYrmMA?si=AKTccJQgYXaokxr8

And wine: Some of Europe’s best wine. But produced in mom and pop wineries so not much exported. Wine is a way of life here. A place where you can take a short trip out to a winery and meet the man and family that makes the wine. Wander the cellars and sample the product … in a beautiful very local and low key setting. Not a wine chateau tour.
https://youtu.be/1AJtDHOJMvk?si=-A05PvtCNYDqpzjS
https://youtu.be/TrfTpCgpUls?si=CjRCDQ-WYeNRSsmz

Beautiful art/interesting historical sites: You will not find a more beautiful city in Europe. That’s subjective so you may find one you think “AS” beautiful. The history here is more recent than many and that makes it more accessible and more relevant in a lot of ways. Communism, russian occupation, holocaust, Austro-Hungarian Imperialism of the 18th and 19th centuries. Easy to understand in today’s terms and fascinating in that some of it is relevant today.
https://youtu.be/QndU3I1mfqo?si=TaIEnhJCxJwbl_lp
https://youtu.be/lZUR-GJLAgY?si=gsYtz3unnfPHPtQ8
https://youtu.be/LEQJpzKqd9I?si=pYrp0bfNwo14xZy1
https://youtu.be/sXBr7lxSVp4?si=ZuJVyG2SG7_mg2IS

Possibility a second destination within reasonable travel distance: 2.5 hours to Vienna for a very different experience or any number of Hungarian short trips.
https://youtu.be/OUuA501Wpts?si=PH-Xk5EHoiBPnBYe
https://youtu.be/pj4EyxKu6vc?si=Hcd9sUpEXVtbMi1z

I'd definitely suggest Verona with a side trip to Lake Garda. You can also get their verona card https://theveronacard.com/ super walkable historic center, fantastic food scene (try the risotto all'Amarone), and amazing architecture. Plus, it's way less touristy than Venice.

I recommend Croatia with a side trip to Ljubljana, the capital of Slovenia!

Or,

Ljubljana, Slovenia and Trieste, Italy

Cuenca and Valencia Spain

Sofia and Plovdiv Bulgaria

Wrocław and Gdańsk, Poland

Marsle, excellent ideas. Especially Sofia and Plovdiv