What to do in Modena for a day?

Both on the same day?

Here are suggestions from Bologna and Modena tourism offices:

https://www.bolognawelcome.com/en/blog/top-10-things-to-do-in-bologna-

https://www.visitmodena.it/en/inspire-me/the-10-must-see-visits-in-modena

We stayed in Bologna for 3 nights. The afternoon of arrival we arranged a private walking tour of the downtown area. The 2nd day we took the Bologna Food & Wine Tour #1 by Italian Days http://www.italiandays.it/ It was an all day tour, starting with pick up in Bologna at 7am, touring cheese factory, basalmic vinegar tasting and Prosciutto Factory. Breakfast and lunch included. It was a splurge, ~$300/person, but it was absolutely worth it, a fabulous experience (you don't need to eat breakfast first and you won't want dinner later). Our third day was rainy so we took the local train to Modena and walked to the Ferrari museum, then to the Market in Modena, that was another great way to spend the day. There are also plenty of things to do, just walking around Bologna.

Assuming you don't have any interest in Italian performance cars I would do a food tour - a good one will include basaltic and Parmigiano Reggiano tasting - check out Mercato Storico Albinelli market, Modena Cathedral and tower and if you have time left check out one of the museums that interests you.

Have a great local dinner maybe at Franceschetta58 if that appeals to you and you can get reservations or check out the later night action on via Del Taglio.

Modena is a great little town with modern tree lined streets, a smaller well defined historic core and real concentration on quality, traditional food.

I enjoyed it as a town and while I stayed a couple of nights it is certainly worth a day trip to visit.
=Tod

Modena's historic center is small and manageable. You can do it in a morning if you're disciplined. Aceto Balsamico tasting near town is worth the detour. Just don't try to do both cities (unless you're comfortable with moving fast and leaving many things behind)

If you have just a day in Bologna, keep it simple: walk under the porticoes, explore Piazza Maggiore, climb the Asinelli Tower for a view (last year it was closed in May when I was there), and be sure to try tagliatelle al ragù or fresh tortellini in a local trattoria.

I was in Modena a few years back. I love motor cars and was only able to fit two of their museums in my day. We also visited two other regular museums, visited a winery and a beautiful bookstore that looks like a cathedral