Barcelona during Christmas!

Just like in any big city nothing tourist attraction is open on Xmas day. You can look up the schedules of the specific places you are trying to go to see if they are open as most publish this on the web. What activities did you have already planned? Do you have a guide book or you can search online "activities to do in Barcelona" and read the many online guides to pinpoint activities that suit your interests.

The churches including the Sagrada Familia are open 9 to 2 Xmas day and the day after

It appears that Casa Batllo may be open on Christmas Day. I didn't attempt to complete a ticket purchase, but the day doesn't appear to be blocked on the calendar. The Casa Mila/La Pedrera calendar doesn't extend as far out as December, so I don't know about that one. The Picasso Museum website confirms that the museum will be closed on December 25 (but apparently open on Dec. 24).

I'd be shocked if any of the major museums are open on Christmas Day.

A quick Google turned up a 2013 TripAdvisor post by Enric (also active on this forum), in which he said Parc Guell and La Pedrera (the latter just until 2 PM) would be open on Christmas Day. That was 5 years ago, so no guarantees that the policies will be the same this year. However, the Parc Guell website currently indicates no closing on Christmas Day.

So it appears you will have multiple options, but note that all of the places I've mentioned normally require pre-purchase of entry tickets to avoid standing in a long line. Given how much else in Barcelona will be closed, Christmas Day might well be very busy.

You should check the official websites of any place you might want to visit on December 24 and 25 much closer to the time of your trip to be sure you are working with the most accurate information possible.

One possibility on December 24: Flamenco concert at the Palau de la Musica Catalana.

Thank you so much!!
We are just starting to plan our itinerary!