Of course, the Spanish are expert protesters, it seems there is some sort of crowd somewhere every weekend. Every now and then there are arrests or an injury, but for the most part everyone behaves.
A bit of very loud whistling.
Some (Communist?) flag waving and chanting. The chants mostly consisted of swearing at the president or simply "Huelga! (Strike!)"
And as you can see, the police weren't particularly concerned either. No helmets or shields. No batons or even intimidating numbers of police. Everyone just sort of does their own thing and then heads home.