Los muros hablan (The walls speak) is a series of photographs made between 2011 and 2013 showing traces of inscriptions left by participants in the 15-M movement, also known as the Indignados, on the walls of financial and political institutions in Barcelona and Madrid during their marches; presented as a transcription, this publication also reproduces the movement's successive slogans. Like an archaeologist of the visible, Anna Malagrida records the traces of conflict, crossed-out or erased writing, on wall surfaces transformed by anonymous participants into spaces of material and symbolic appeal; though the foot of these street walls and their apparent monumental power speak of an unequal struggle, the author photographs them while they still carry the remains of the inscriptions, the photographic act becoming a gesture of resistance, the recording of these traces and the restitution of messages and voices functioning as an archive of a collective movement that questioned its own notion of representation.