The aim of this urban project is to investigate the relationships between the physical metamorphosis of an existing urban landscape and the shift in its environmental qualities and social relevance. The project site is the Porta Genova railway station, in Milan, which presents a criticality currently not resolved: the rail yard cuts the urban pattern dividing in two part the neighborhood. The design program will include a student hostel, services and a multi-purpose space for events and expositions, moreover the creation of a meaningful public open space in the form of a new unique surface. What we call urban design could be seen as an act of "grafting" a new organism onto an existing one, introducing a new physiology in an existing pattern.