Luzinterruptus.

Luzinterruptus is an anonymous artistic group in Madrid who seek to highlight problems within the city using a wide variety of temporary light-based installations. The group is headed up by a duo including an artist and a photographer who have been using their art to create awareness of social and environmental issues since 2008. Via their website:

We began to act on the streets of Madrid at the end of 2008 with had the simple idea of focusing people´s attention by using light on problems that we found in the city and that seem to go unnoticed to the authorities and citizens. But everything that we do does not have a subversive aim. Sometimes we simply want to embellish, or to highlight anonymous places or corners that seem special or objects to which we think extraordinary artistic value, although they have been left on the streets for unknown seasons, with artistic intention, by anonymous people. (by Christopher)