200 years ago, this spot was in a riverbed. The island of Paparinemo was the rocky area up the stairs; it sat in a triangle between present-day Broadway, 231st Street, and Tibbett Avenue. Immediately to the south is Marble Hill, another, more famous, NYC geographic oddity. Even though it lies north of the Harlem River, i.e. on the Bronx side, it is part of the borough of Manhattan.
The Harlem River used to run around to the north of Marble Hill, but it was straightened in 1895, when a ship channel was dug below Marble Hill. Thus, in this photograph, the borough of Manhattan is on both sides of the river, Marble Hill to the right, Inwood to the left.
The Kingsbridge Armory