Monserrat

We took a day trip there and highly recommend it if you have the time.

You can check our this website for more info.

You can simply go to the Placa d'Espanya train station (located underground, I believe) and get tickets there. (You'll probably be buying a round-trip ticket; be sure you're clear on that so you don't end up buying an unnecessary ticket back from Montserrat to Barcelona.) I think you have to make a decision about how to handle the second leg of the trip, because there are two transportation options. I haven't been to Montserrat myself, so I don't know the details.

Rick's guidebooks are excellent for advice on this sort of thing. I highly recommend either the guide to Spain or the guide to Barcelona, depending on how wide-ranging your trip is.

The Picasso Museum has good coverage of the artist's early career. It tends to be an absolute zoo. I wouldn't count on getting in without a pre-purchased ticket. However, you might well have time to see Montserrat in the morning and early afternoon and then hit the museum after returning to Barcelona. It's open until 7 PM. The museum is closed on Mondays; check the museum's website to be sure it won't be closed on any additional days during your visit.

I've been to both, and if I had to pick one, it would be Monserrat. It's an easy train ride from town. Take the cable car up and down - unforgettable! If you attend mass, the ushers will throw all of the tourists out, and you will have the place practically to yourself. Then do some hiking up the hill; have a picnic. Great day trip.

If I could only do one, I’d visit Monserrat. We took the train and then the cable car to the top. I enjoyed the Picasso museum but enjoyed Monserrat. In the Picasso museum I liked his renditions of Velázquez’s Las Meninas most.

We are just returning from our trip from Barcelona. Our trip to Montserrat took the entire day. We hiked the way up And took the rack rail down. It is very easy to get to from Espanya. There are hourly trains. I believe that the funicular is closed for maintenance till Feb? When we bought tickets, they had a sale combining the ticket to Montserrat and the rack rail even though we did it only one way.
Picasso museum was a good afternoon as well.
Have fun

If the cable car is too busy you can always take the train. The views are just as lovely and it's definitely more relaxing and you can sit down. My vote is for train-especially as I saw the wait for the cable cars. Both are enjoyable and do walk and hike around the paths. We got some wonderful pictures overlooking the valley below. May not be great if you are afraid of heights but so worth it for the views. Probably the most beautiful part of Barcelona area.

We were in Montserrat in 2012 so it may have changed but a highlight for me was to take the tram down the hill a bit to the stations of the cross. Each station is by a different artist and at the end there was a little chapel where mementos of people being prayed for are left.

Another vote for Monserrat if you have time for only one. we were there in Sep 2022 and it was an almost full-day trip for us. We hiked up and had a quick sandwich lunch. A memorable day indeed.

A post I published a while ago, but still 100% valid:

https://community.ricksteves.com/travel-forum/spain/a-visit-to-montserrat-the-holy-mountain-near-barcelona-in-catalonia

and if visiting by car, you might want to explore other nearby gems: https://community.ricksteves.com/travel-forum/spain/monteserrat