Barcelona Day Trips using the Train

We took the train down to Tarragona for a day trip, it's about 1.1/2 hrs. They have a Roman Coliseum and a Beautiful Roman Aqueduct that are worth seeing. The old town part is fun to roam and there is a museum that we enjoyed. Also, there is a beach for swimming and sun bathing, these are all near the train station and easy to walk to except for the Aqueduct.

Girona is a nice city to visit, but if you have the time, I’d recommend staying a few days (or at least an overnight)

Enjoy your trip!

Edited to add:
You may find this thread helpful: Montserrat or Girona

Girona is my favorite option from Barcelona (haven't been to Tarragona), but there are many other options. You'll probably find a bunch of useful posts if you search the forum for Catalunya.

Depending on your interests, you might consider Figueres (beyond Girona; location of the Dali Theatre-Museum), Sitges (artsy, funky beach town; could be a different experience on weekdays vs. weekends in October) and Reus (just outside Tarragona, with several interesting examples of modernista architecture).

We did Girona and Montserrat.

We went to Montserrat. It isn't a city or town, but it is one of my favourite day trips ever. It's a breathtaking place.

We did Tarragona and Manresa in October 2022. We are heading back to Barcelona in three weeks via Girona for two nights and are planning to go to Montserrat.

Tarragona was lovely. Beautiful walk around the old city walls, lots of Roman ruins and lovely tapas near the cathedral. We enjoyed it so much that we are staying there for two nights soon on our way to Valencia from Barcelona.

Manresa was interesting as it is the end of one of the pilgrimage walks - the Caminoa de Sant Ignacio - and had a nice Roman bridge and interesting basilica. A few modernista buildings. We wanted to see a Spanish town without the tourists and Manresa fit the bill perfectly.