150 ravines, 1,200+ km of edges
Toronto's Ravine System
Hidden beneath the street grid is the largest ravine system of any city in the world — 30 times the size of New York's Central Park, and within a 10-minute walk of nearly a third of Toronto residents.
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Most visitors never see it, because it's built to be invisible from street level — but Toronto sits on top of the largest ravine system of any city in the world, a hidden second landscape running underneath the grid.
The scale of it
The system includes at least 150 individual ravines, protected under the city's Ravine and Natural Feature Protection Bylaw across roughly 110 square kilometres (42 sq mi) of public and private land — about 30 times the area of New York's Central Park. Measured by edge length rather than area, the ravines add up to more than 1,200 kilometres, roughly ten times longer than Toronto's actual Lake Ontario waterfront. Close to a third of the city's population lives within a 10-minute walk of one.
How old it is
The river valleys that became these ravines started forming around 12,000 years ago, as glaciers retreated at the end of the last ice age. Archaeological evidence shows humans occupying parts of the ravine system as early as roughly 9,000 BCE — making it, in a real sense, the oldest continuously used part of the city's landscape, well predating even the Indigenous history covered in our other guide.
What they actually do
Beyond recreation — over a million people a year use the ravines to hike, bike and explore — they function as a working watershed system: filtering and slowing stormwater, supporting biodiversity that can't survive on the paved surface above, and measurably reducing urban heat. The most developed and accessible stretch is the Don Valley, but the system extends into ravines across almost every part of the city, including many with no formal park designation at all.
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Sources
- Wikipedia — Toronto ravine system
- Curiocity — Toronto Is Home to the Largest Ravine System in the World
- City of Toronto — Ravine Strategy