What is Barcelona's culture?

Answer 1

Castilian and Catalan

Castilian, also means Spanish, is the culture one would usually associate with most of Spain. It's also fair to call it simply Spanish. This is not the indigenous culture to Barcelona, but many Spaniards have migrated to the city.

Catalan, a regional culture in eastern Spain. The Catalan people speak their own language (called Catalan) and usually speak Spanish too. Catalan and Spanish have many similarities, but are clearly separate languages, and it is argued by many that Catalan is closer to French than to Spanish. Catalan culture shares many things with that of southern France.

Further Reading, on Wikipedia:

Spanish Language, Catalan Language, Barcelona, Catalonia, Valencia, Spain