From the Detroit River Front Website:
The Dequindre Cut Greenway, an urban recreational path, officially opened to the public in May of 2009. The 1.35-mile greenway, developed through a public, nonprofit and private partnership, offers a pedestrian link between the Riverfront, Eastern Market and many of the residential neighborhoods in between.
Formerly a Grand Trunk Railroad line, the Dequindre Cut is a below-street level path that runs parallel to St. Aubin Street, between Mack Avenue and Woodbridge Street just north of the Riverfront. Well-known for its urban artwork and graffiti, the first completed section of the Dequindre Cut is between Woodbridge Street and Gratiot Avenue. The greenway features a 20-foot-wide paved pathway, which includes separate lanes for pedestrian and bicycle traffic. Entrance ramps to the Cut are located at Lafayette Street, Gratiot Avenue and at Woodbridge Street.
You can find out more by visiting: http://www.detroitriverfront.org