Sitting on this square is the Church of Sant Felip Neri, which Antoni Gaudi attended. You can see ample evidence of shrapnel damage on its facade. This was incurred during the Spanish Civil War. Barcelona was a stronghold of the (anti-Franco) Republicans so there was a lot of activity here during the war. This church shows the collateral damage inherent in fighting: the church wasn't the target of the attack; a nearby Catalan government building was. But the church saw shrapnel nonetheless.