2 Days in Barcelona - What are the must-dos?

https://www.cntraveler.com/gallery/best-things-to-do-in-barcelona

Amazing thing Google…

Hop On Hop Off Bus .......
Possibly would give you a good overview of the city

Get a selfie on the Rambla standing with the neon-green-vested police holding machine guns.

Get some good cheese in the Boqueria

Rick Steves has suggested itineraries:

https://www.ricksteves.com/europe/spain/barcelona-itinerary

If you see only one thing in Barcelona, visit the Sagrada Familia. Amazing building that you will never forget.

We were in Barcelona just last week. We were there for just under 48 hours.The " must sees" are the Sagrada Familia, Parc Guell, and Casa Battlo. We also saw La Pedrera, and the Picasso Museum ( mainly has lesser known works of his from when he was an art student but also has a few paintings from his Blue and Rose Periods.) There is also a series of Cubist style paintings based on his interpretation of Diego Velazquez's famous painting Las Meninas. We also visited the Palau de La Musica Catalan which is basically a concert hall with amazing interior design. We avoided walking around Las Ramblas and the Bari Gotic neighborhood due to increased pickpockets and we preferred to visit sites rather than just walking around.

Las Rambles to us was worth the experience but be super careful for pickpockets!!! We much preferred the Barcelona Cathedral and being able to walk around the turrets and seeing the geese inside very unusual. La Sagrada Familia is a sight to behold and is worth at least walking around outside. Good luck and enjoy!

But be aware that there are a bunch of popular sights in Barcelona for which you have to get your tickets in advance unless you're good with potentially spend hours of your very limited time standing in a ticket line. There are the biggest problems:

La Sagrada Familia
Parc Guell
Casa Mila/La Pedrera
Casa Batllo
Picasso Museum
Palau de la Musica Catalana (the English tours sell out)

You should expect the first 5 to be mobbed beyond belief.

I like @acraven's list for sites to visit.

We did the Palau de La Musica Catalan tour, but then returned for an evening show. That was really a great "extra" to see it with a guide during the day, but then to "experience" with an orchestra and folks in the seats. Definitely a great way to see it and maybe a highlight of the non-Gaudi sites.

We had more than 2 days there, so there is probably a good bit of time constraints for you, but while we did a lot of the Gaudi homes and buildings - all unique and worthwhile - we also just did a lot of walking and a LOT of pintxos grazing every evening. Picked a couple bars that had a nice selection and just nibbled and drank and people watched. Lovely way to spend some time.

Absolutely Sagrada Familia is "must", but don't go "full Gaudi" at the exclusion of other things, and we've now been to MANY Picasso museums around Europe, and time permitting, it's a great add to your visit, but you may be like us and have seen his work many many times and can prioritize it differently in lieu of other opportunities. If I was culling my Gaudi list, I would drop Park Guell (likely fairly swamped) for a guided (human or audio) interior tour of one of the homes he built.

Besides walking everywhere, so you get an on-going tour of the core city by default, we also took a fun guided bike tour that extended our range a little bit. A couple hours meandering around Barcelona from up at Sagrada Familia and down to the waterfront beaches. Definitely a nice way to cover more area in less time, and it took in the EXTERIORS of most Gaudi homes/buildings, so you at least get familiar with where things are situated.

Visit the Sagrada Familia and explore the Barri Gòtic.

@tomR what show did you see in the evening. Was there something you couldn't see during the performance if you had to visited in the morning?

Just some ideas that we personally enjoyed:

Sagrada Familia (reservation process)
Barri Gotic
Montjuic Hill (Olympic Park/Gardens/Castle)
Cuitadella Park
Drinks at top of W Hotel on beach (if you still can do that--we went many years ago)
Barcelona Cathedral