Among the most pressing and significant challenges for the environmental movement today is the notion of metamorphosis - the rebirth and making whole the degraded and forgotten places of our cities. Such is the story of the Don River in Toronto, a once beautiful and ecologically productive river valley that over a hundred years or more has been degraded and largely destroyed by industrial development and the encroachments of an expanding city. The process or urban growth ignored its natural heritage in many ways. Its once productive estuary marshes and waters that teemed with life were replaced by an industrial port; its natural meanders and floodplains were straightened to accommodate shipping access upstream; the valley was denuded of vegetation and transformed into an expressway transportation route; the neighbourhoods that surround it turned their backs on a natural setting that has become a gap between places, not a place in itself; and the valley bottom became a convenient dumping ground for hydro towers, transformer stations, pipelines and the detritus of the city. Yet the citizens of Toronto, led by a group naming themselves the Task Force to Bring Back the Don have initiated an ecological and political process of restoration and renewal, that over time will bring back life and health to the river. It is an act of faith and an inherent recognition of the right or urban people to a healthy and sustainable environment. This paper explores the fundamentals of this story: its connections with future communities planned on its lower reaches (the subject of our second paper); the common problems of repairing past industrial devastation; the political partnerships required to implement the plan; and the principles on which the vision has been based and which link our two studies - the nature of renewal.