Book 25, Question 93
Why does Toronto have so many hidden forest valleys?
Toronto sits on soft soil left behind by glaciers.
Rivers such as the Don and the Humber have carved deep valleys called ravines into this soil over thousands of years. Because the steep slopes were hard to build on, many were left wild and became forests. Today the ravines cover about a sixth of the city and are home to foxes, owls, and wildflowers.