A hidden wilderness within the city
I still remember the first time I truly experienced Toronto’s ravines. It was after a long day of site visits. On a whim, I decided to walk from the city center toward one of the green corridors I had seen on a map. I followed a small, unofficial trail alongside a highway – hardly a scenic route – until the roar of traffic faded and the ground dipped downward. Suddenly, I was standing at the edge of a forest.

Within minutes, the city disappeared. The air felt cooler. The sound changed from engines to birdsong and flowing water. I even saw deer moving quietly between the trees. It was as if I had crossed an invisible threshold into another world – one that existed entirely within the city, yet utterly apart from it. During my walk, I was so excited that I had to text my colleagues who were walking around the city center: “I have seen deers, turtles, black squirrels, birds, and a tree that was taken down by beavers!” It was amazing.

That experience changed how I understood Toronto. The ravines are not an “amenity” to be visited, but a parallel world – an inner landscape that allows the city’s residents to lose and find themselves at the same time. You walk down into them, leaving behind the noise, the heat, and the density. And for a few hours, you can move through something as raw and alive as any wilderness.

Nature as design – and beyond design
As a landscape architect, I am often asked what the perfect nature-based urban design looks like. In Toronto, the answer is already there. The ravines are the most beautiful design one could imagine – and yet, they were never designed by humans. Their form is geological, hydrological, and ecological. It is the form of time itself.

At SLA, we have often looked to the ravines as inspiration for our work in Toronto. In our transformation of 520 acres of the former Downsview Airport – once an active airfield, now set to become one of Canada’s largest development sites – we studied how the lost creeks and ravines could be reconnected within the new neighborhood. The result is a framework plan with nearly 100 acres of new public green space with a two-km Green Spine – an extensive blue-green infrastructure system – that threads nature through every block, street, and rooftop. All of it is stitched together by an “inconvenient” network of nature corridors. The goal was to weave nature back into the urban structure – to bring the ecological logics of the ravines into the built environment’s rigid grid structures.

Downsview is an attempt to learn from what the ravines already know: that the health of a city depends on the health of its natural systems.

A system of life – and inequality
Of course, the ravines are not without their challenges. Many of them were once used as backyards for infrastructure – places for fences, garbage, and neglected maintenance. Some remain difficult to access, particularly for those living in less affluent neighborhoods. Historically, the city’s wealthiest residents have lived closest to the ravines, enjoying private access to their beauty, while others have been cut off from it by roads, railways, or simply a lack of paths.

But this imbalance also points to opportunity. Imagine a future where every Torontonian can walk or cycle from their doorstep into the ravine system. Where each neighborhood has a direct, democratic connection to this green network. Improving access – both physical and social – is one of the great design challenges and potentials of the coming decades.

Ecological and social infrastructure
The ravines are not just natural; they are infrastructural. They regulate floodwaters from the north, filter runoff before it reaches Lake Ontario, and moderate the city’s heat island effect. During summer heatwaves, temperatures in the ravines can be several degrees lower than the surrounding streets, providing natural cooling and relief.

They are also cultural and recreational infrastructure. You can run, cycle, or ski through them. You can escape into them for solitude or share them with friends. They give the city both resilience and joy – the two things every urban environment needs most.

And they are ecological infrastructure. Every year, 13,194 tonnes of carbon are sequestered by the ravine forests. Salmon swim upstream through their waters, linking the Great Lakes’ vast aquatic systems with the city’s inner life. It is a breathtaking example of how an urban region can function as an ecosystem, not just as a collection of buildings.

Restoring what was lost
Toronto once had hundreds of creeks and tributaries feeding its ravine system. Most have been buried or piped underground over the past century. This was done in the name of progress – to control flooding, to build roads, to make room for the city. But we now understand the cost. The paving of these waterways has made Toronto more vulnerable to flooding, degraded habitats, and disrupted the delicate balance that the ravines depend on.

We thought we were smarter than nature. We weren’t.

Today, Toronto’s planners, ecologists, and designers are working to reverse this – to “daylight” creeks, restore wetlands, and rebuild the connections between the city’s water systems and its urban fabric. It is a humbling, but hopeful process: an urban design practice that starts by admitting that nature knows more than we do.

The true icon of Toronto
In a century defined by ecological crisis, the most powerful urban icons will not be monuments of stone or steel. They will be systems that sustain life – networks of green and blue that make our cities breathable, liveable, and humane.

Toronto’s ravines are exactly that. They are both symbol and structure, beauty and function. They connect the city’s past to its future, its nature to its people, and its grid to its flow.

For me, they are the most honest expression of what an urban icon can be: not something we build to show our power, but something that helps us more than we help it. Something we must appreciate, acknowledge, and live up to.

This article was first published in the December 2025 issue of Topos: Urban Icons