Harsimus Branch Embankment

From their website:

The Harsimus Branch Embankment is a massive, segmented stone structure that runs for six blocks through Downtown Jersey City parallel to Sixth Street.

Part of the once-mighty Pennsylvania Railroad freightway, the historic Embankment played a key role in shaping the Downtown and in the development of the Port of New York and New Jersey. The Embankment is listed on the State Register of Historic Places, is eligible for the National Register, and is a Jersey City Municipal Landmark.

The Pennsylvannia Railroad Harsimus Stem Embankment Preservation Coalition has an extensive website. There is also a Wikipedia page with some history, as well as links to previous press stories.