“There are two side platforms. There is no crossover or crossunder, and no mezzanine. The PATH tracks, which were built forty years before the Sixth Avenue Line, are behind the platform walls. The Sixth Avenue express tracks are underneath the PATH tracks and were constructed using the “deep-bore” tunneling method in the mid 1960s. Neither the PATH tracks nor the express tracks are visible from the subway station.

“Each side of the station has four street staircases and a direct indoor entrance to the 23rd Street PATH station. Two of the four entrances on each side appear to be part of the original 1911 PATH entrances. The tile band is lime green. The tile band on the track walls appears to be obscured by support beams directly underneath 23rd Street.”

- The unexpectedly well-written Wikipedia entry for 23rd Street (IND Sixth Avenue Line)