I live in Barcelona, it's a very pleasant city (if you can aford to live here), The city has almost 2000 years of history and architecture. It's inhabitants left its mark. Eixample (the Extension) was planned kinda all at once by Cerda and thats why theres an over representation of specific styles of architecture, and why Eixample feels a bit like an open air museum.

https://www.youtube.com/watch?v=YfN517mqhC8 (Absolutely worth watching if you want to know why Barcelona was planned the way it was.)

If you go to the "Gothic quarter" or to Gracia you won't see much "Art nouveau."

Its a very varied city. I live in a building in the "Modernisme" style and its lovely.