This book deals with the re-appropriation of urban space from the homeless peoples and prostitutes point of view - what is the relationship of these people who live in the Fourth World with urban space, what is different from what we know, their relationship with the First World and the inability of society in integrating them. The NGO Mdecins du Monde defines Fourth World as people in situations of extreme marginality due to a disability or a need which affects both dignity and rights of any human being. The artists Lara Almrcegui, Antoni Abad, Matas Costa, Shole Hejazi, Juan Lpez-Aranguren, Rubn Lorenzo y Fernando Menndezthrough media such as video, photos, net-art have re-interpreted an anthropologic study on marginality in Madrid.