Planned and spontaneous demonstrations take place in Spain, especially in Madrid and Barcelona, in response to economic or other events. If you encounter a large public gathering or demonstration, the U.S. Embassy suggests that you avoid the area. Even demonstrations intended to be peaceful can turn confrontational and escalate into violence. You should avoid areas of demonstrations, and exercise caution if in the vicinity of any large gatherings, protests, or demonstrations.
The Government Delegation in Madrid has authorized the following demonstrations:
08/25/2016 20:00-21:00 Plataforma contra la impunidad de los crimenes del Franquismo, Against the impunity of Franco, Puerta del Sol
Source: Overseas Security Advisory Council