“Caja Negra”, or Black Box in english, is a photographic project about the traces in the urban space. The city is a being who builds itself and his perpetual transformation objectifies, among other things, in the stratums of which she is composed of and his own deterioration. This work is focused in the representation of the skin of the city, understood to mean a memory surface. There is a parallelism between this and the photographic process: a way to capture the memory in a physical surface. What is ephemeral, what it is not already visible, is nevertheless represented and convert into matter. The title of “Black Box” is a reference to the photosensitive process, originally derivative from the camera obscura.