St. Patrick's Cathedral is the site of three survey marks—two of which date from the historic NYBE+A leveling survey of the early 1900s. The first mark we searched for at the cathedral was this chiseled T. The search took longer than I expected, mainly because at first we were searching the wrong pillar, and because the correct pillar was obscured by scaffolding.
I was still poking around in the wrong spot when Rich found the T. But it was up to me to shimmy behind the scaffolding and attempt to photograph the mark. All the while, a cop (yes, the one in the third photo below) was watching my every move. '"It's a bench mark," Rich explained to him. He peered in with a slightly raised eyebrow and then left us alone.
The original description (from Precise Leveling in New York City [1909-1914]) is as follows:
B. M. 825—Fifth Avenue. The center of the horizontal bar of a T cut in the south face of a granite pilaster on the south side of the main entrance to St. Patrick's Cathedral on Fifth Avenue, between East Fiftieth Street and East Fifty-first Street. The bench mark is about 83 feet north of the north line of East Fiftieth Street, is 2.3 feet above the walk and 1.8 feet from the west side of the pilaster. Elevation, 80.965 ft.