Let's try this one again!
The John T. Brush Stairway runs through Highbridge Park from the top of Coogan's Bluff at Edgecombe Ave. down to the Harlem River Drive below at about 158th Street. The stairway is closed off now, as it is in disrepair, but for the first half of the 20th century it served to carry people down to the Polo Grounds, home to the baseball and football New York Giants as well as the original home of the New York Mets. The original home of the baseball Giants, 111th Street between 5th and 6th Avenues, is close to where I live.
John T. Brush owned the Giants from 1890 until he died in 1912. The original Polo Grounds at this location was a wooden structure that burned down on April14th, 1911. Brush rebuilt the stadium in concrete and steel in time for the Giants to play the Athletics in the 1911 World Series. Incredibly, the new stadium was sufficiently completed that it opened on June 28th. The stairway is the last remaining part of the stadium.
I discovered it years ago on my first bike ride to work after moving into the city. I had taken the wrong turn and, being the stubborn sort, found it more acceptable to climb up the stairs than to backtrack. Having to toss your bicycle over a fence is not the greatest feeling in the world.