. The use of these areas as alternatives to traditional urban open space has been promoted in response to the need to re-establish a rapport between city dwellers and "nature". In fact, in these areas it is possible to experience exploration and play, contemplation and reflection, in ways that are otherwise unfeasible in a metropolis. Such practices are institutionalizing urban wilderness as a new and distinctive kind of public space. However, the significance of urban wilds goes beyond their ecological and recreational value. We believe each remnant of wilderness in Northern American cities is a semantic reservoir, a place where the meanings that Northern American culture has attributed to nature manifest within an otherwise all-encompassing urbanity, islands of intense placeness emerging from the endless stretch of sprawling development. As the expansion of Northern American urban areas relentlessly continues, and cities further transcend the dimensional scale that had characterized them throughout history, urban wilderness remnants acquire immense relevance. In the synthesis of their ecological, functional, and semantic value, they become primary elements of the dispersed, polynucleated, territorial urban systems of tomorrow, capable of structuring the form and fostering the sense of place of the city in which they find themselves. This dissertation intends to develop this thesis by undertaking a study of the semantic substratum of the idea of wilderness in Northern America, and an exploration of the places within major Northern American cities that most vividly evoke such substratum.The work is composed of two parts. The first chapter of the first part examines the history of the idea of wilderness, the transformations of its connotations, and its significance in Northern American culture. The second chapter deals with the ambiguous meaning of the word natural and with the consequences of such ambiguity, and the dilemmas associated with the oxymoronic proposition of managing the wild as well as the conflicts related to wilderness preservation. The third chapter offers a tentative definition of urban wilderness and undertakes a description of its recurrent characteristics, developing a classification of wilderness remmants in the city. The second part employs the taxonomy created in the third chapter of the first part to examine fifteen case studies. Ordered in five chapters according to their dominant original landscape.