Gaudi makes Barcelona interesting to see but Barcelona itself is overhyped with little to see beyond Gaudi's works.
In the whole of Spain, the south has a significant history with a lot of historical buildings and very old city centers. Sevilla especially, but Granada or Cordoba are gems too - and I'm skipping lots of smaller cities or villages like Ronda, Setenil or Toledo more in the north, each more interesting than Barcelona. Unless of course the goal is to party, then none of the previous villages are very appealing :-)
Barcelona is interesting for its modernity and city design.
It's maybe the most heavily planned and designed European capital.
Maybe it's hard to see that coming from the US where all the cities have been planned in the last centuries and you are used to see blocks everywhere, but in Europe it's the exception, and the way it have been done in Barcelona is, I think, unique in the world.
If you don't know the concept of superblocks, there you go : https://www.citiesforum.org/news/superblock-superilla-barcel... but to summarize, Barcelona have been divided in superblocks containing blocks. Inside those superblocks, there are less cars and inside the blocks, there are barely any car at all. What that means is that each superblock is like a little city and each block is like a peaceful village. Hundreds of peaceful places inside of a busy european capital.
Superblocks are often mentioned in the context of Barcelona, and while a good idea in theory, in practice a lot of locals are against it.
It would be fantastic if the whole city was implemented using superblocks, but the reality of it is that the areas where superblocks have been planned go up in price, pushing out low earning locals and bringing in foreigners who can afford it.
This might have been ok for a while in areas like Poblenou which were extremely underdeveloped 20 years ago (mostly industrial buildings) but even the new incarnation of superblocks (green axes) which are mostly about pedestrianization of streets and squares always results in rent increases.
There's no good solution, I would like to see a modern city built with pedestrians in mind from the get-go though.
The idea that we should purposefully keep places worse to live in so the rents stay cheaper is… what it is I guess. I can empathize but I can’t accept it. Improve everything.
There are other things to see beyond Gaudi -- and he's not quite such a unique outlier as you might be led to believe! Gaudi is justifiably the most celebrated and well-known, but he was part of an architectural movement, not just a solo genius.
For example, the Palau de la Música Catalana is amazing, and has lots of the fluid forms and nature iconography you might have assumed was unique to Gaudi, but it's by a different architect (Domènech i Montaner, says wikipedia).
In the whole of Spain, the south has a significant history with a lot of historical buildings and very old city centers. Sevilla especially, but Granada or Cordoba are gems too - and I'm skipping lots of smaller cities or villages like Ronda, Setenil or Toledo more in the north, each more interesting than Barcelona. Unless of course the goal is to party, then none of the previous villages are very appealing :-)