Many cities have built-over waterways running beneath them. London has the River Fleet, Toronto has Taddle Creek, and Peterborough has Jackson Creek, which runs under the downtown core before draining into the Otonabee River. Back in September 2004, construction on Hunter Street West exposed that section of Jackson Creek to the light for at least a short time. Fortunately, from the environmental perspective, unlike the other two examples, Jackson Creek isn't used as a sewer. As far as I know.
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