Parc Guell vs Casa Battlo?

I'd choose Casa Batllo. Actually, my preference would be Casa Mila/La Pedrera rather than Casa Batllo. Based on my 2016 experience, I think there's a possibility Casa Mila will be 5% less crowded (though both will be unbelievably packed), and I just found it that much more interesting. There's nothing wrong with Casa Batllo except the crowds (and the price is steep), though, so I'm not discouraging it.

Parc Guell is definitely worth seeing, but it takes longer to get up there, and there's a possibility (however slight) the day of your prebooked visit might be less than ideal, weather-wise. Anyone who has a significant problem with severely crowded conditions should definitely choose Parc Guell. It, too, will probably be mobbed, but it's outdoors.

If you're a bit nervous about needing to prebook multiple sights during a short visit to the city (and it is tricky): There's a lovely former-hospital complex designed by a different architect, Lluis Domenech i Montaner, that can be visited without the hassle of prebooking an entry time. You can walk right up to the ticket counter and buy a ticket. It's Recinte Modernista de Sant Pau, and it's not terribly far from La Sagrada Familia. No preplanning required, but it is a multi-building complex that takes time to see (multiple hours, ideally, even if you don't stop to read the extensive posted explanatory information about the hospital years. https://santpaubarcelona.org/en/

My pick would be Casa Batllo, mostly for the reason there's just so much more to see if you like Gaudi. The park has some interesting architectural features but most of it is just a park (a very nice one, with great views, of course). With Casa Batllo each room is interesting in a different way. I also really enjoyed Palau Guell. But really you are spoiled for choice in Barcelona with modernist architecture.

Casa Battlo's rooftop is reason enough to visit. Then, there are the immersive experiences and, of course, the rooms. That this was someone's home makes it even more enjoyable. Make sure, if you go, that you have your photo taken where a photographer is stationed. It is more expensive than Parc Guell if cost is a concern. I have been to PG three times and enjoyed it very much, but weather is a factor--last time in December 2025, it was raining and had been raining for days before. On the other hand, CB was cheek to jowl with people, but that may have been because it was just after Christmas with many off from school and work. You are spoiled for choice in Barcelona. Enjoy!

Easy choice for me is Casa Batlló. We actually did one of their “golden nights” flamenco concerts on the roof and had a beautiful evening. It was a bit of a “battle of the bands” as the thumping dance music from a nearby rooftop club filled the silences :-)

If you want to sneak in an easy third site, the Hospital Sant Pau is a very short and pleasant walk from Sagrada. There is never a line there despite it being a really impressive campus of moderismo buildings. You don’t have to see it all if you’re short on time. It’s much more compact and doable than Park Guell. And like I said - very convenient for you.

Another vote for Recinte Modernista de Sant Pau. Gorgeous architecture inside and out, and not crowded at all. I had a short time in Barcelona and had read that Park Guell was a bit of a logistical hassle, so I opted to skip it.

I went to Casa Mila instead of Casa Batllo. I had read that it was a bit more of an instagrammer "scene" than Casa Mila, so I chose Casa Mila. I went at earliest entry times and it wasn't crowded (this was in early February, though).