If you really want to impress the locals of Barcelona when you visit, try pronouncing Casa Batlló in Catalan: [ˈkazə βəˈʎːo]. In case you're not familiar with the international phonetic alphabet, it sounds a little bit like "Casa Bal-Yo." You'll also get away with pronouncing Casa Batlló like "Casa Batch-Yo", but if you say "Casa Battle-Oh" you might get some quizzical looks!