The modern city always exerts a semiotic bombardment: we are surrounded on all sides by a pictographic labyrinth, whether in notices, posters, graffiti or advertising. But with the use of digital cameras and GPS receivers, this bombardment can be turned into a tool for creativity, for the pursuit of chance associations and synchronicities. In "Signs of the City," teenagers and young adults in Barcelona, Berlin, London and Sofia do just that, with the aid and encouragement of professional artists. The book is the result of a project that lasted one year, incorporating workshops, online activities, conferences and exhibitions, and that initiated a network between over 30 institutions. The perspectives that emerge from the lenses of these teenagers and young adults are of course fresh and surprising, and offer new takes on the four European metropolises, through the most innovative possibilities of data processing.