For the Midwestern metropolis of Chicago, the city’s face is the shore of Lake Michigan, an inland sea lined with freshwater beaches within walking distance of downtown skyscrapers. Chicago’s namesake river used to flow into Lake Michigan but by 1900 was carved into a canal and had its flow reversed, taking water out of the lake, flowing southwest in a series of canals that fed into the Mississippi watershed.

One reason for this massive engineering project was the South Fork of the South Branch of the Chicago River, better known as Bubbly Creek. Subject to pollution coming from the country’s largest stockyard, this hidden waterway is Chicago’s version of Brooklyn’s Gowanus Canal. The above photo shows the rail bridge carrying the Heritage Corridor commuter line across the creek.