When you usually turn on the news and see protests in Europe these days, it’s generally about austerity measures. Spain, though, is having a bit of a constitutional crisis (on top of those austerity protests in Madrid): Catalans are pushing for independence. So, if you’re in Madrid, you protest the EU’s austerity measures; if you’re in Barcelona, you protest Spain.
A lot of this is tied into economics (Catalans think they can do better on their own and resent the “high tax rates” they pay to the Spanish government), but Catalonia also has a very distinct identity, and in many ways, recent events trigger some pretty important historical memories.
After all, the last time Catalans tried something like this, it sparked that brutal little thing known as the Spanish Civil War.