If you were a city planner in one of the great cities of our Earth and you discovered that a railroad right-of-way had been abandoned and would never be used again what might you do? Perhaps if you knew your stuff you'd convert it into a 4 mile long park, about half of which is elevated above street level on the old rail viaduct. This long narrow park pretty much allows the visitor to walk in carfree bliss from Place de Bastille to the Bois de Vincennes.