Walnut Street Bridge

Not a park by area - the city calls it a linear park and publishes no acreage - but it is 2,376 feet of public space over the Tennessee, which is close to half a mile and among the longest pedestrian bridges in the world.

It was built in 1890 to a Pennsylvania truss design by Edwin Thacher, made by the Smith Bridge Company of Toledo, and closed to vehicles in 1978. What happened next is the reason it is still standing: a group of private citizens organised to save it and raised over ten million dollars for a complete rehabilitation. It reopened in 1993.

It is the connection that makes the rest of this list work on foot. Coolidge Park is 0.56 miles from the far end, Ross's Landing 0.42 from the near one, and the Riverwalk runs under and past both.

No hours, no fee, and the city's own size field for it reads "2.376 sq feet", which is a typing error rather than a very small bridge.