Constancy is not the goal of sustainability. Constancy is impossible.
- Richard T. T. Forman

Toronto is often called a city of ravines. In their depths, they are repositories of urban infrastructure: always densities of natural landscape, they are also often the hosts of built urban necessities. We live near the Cedarvale Ravine, once cut by the Castle Frank Brook and part of the Don River watershed; the stream’s long gone – under its floor the ravine is now home to trunk sewer lines and a stretch of the Spadina subway, Bathurst Street flies overtop. While it’s not an ideal co-existence – the fill over the buried lines, for instance, doesn’t drain properly, the ravine is a reasonably successful example of urban adaptability. Flush with wildlife and vegetation, it is the place to find a good chunk of the local residents on the weekend.

The long-term sustainability of the city depends on the co-operative existence of its infrastructural systems - layering them at both the larger regional scale and the smaller neighbourhood scale so that we largely retain the remaining corridors and pockets of nature the City was built on and around. A good number of these areas of the City were buried or cleared out in the past so that they could be (almost) completely built over – as the City is developed further, Cedarvale provides an example of how a natural and built urban landscape can be better integrated.