Is it true that a stream flows under the Empire State Building?

Quite true. High-water marks made by workers in the building's sub-basement show that the stream beneath it has risen as high as six feet in the spring, after a snowy winter. One of Manhattan's many original watercourses, the now-covered stream cuts through the southwest quadrant of the building. It is clearly visible on Viele's 1874 map of Manhattan waterways, rising in what became Times Square, flowing southeast and then out into the East River at Kips Bay, around 34th Street. The stream proved a headache for the engineers of the Pennsylvania Railroad tunnels, and for the builders of the old Waldorf-Astoria Hotel on the site of the Empire State Building. It is one of many underground streams in Manhattan that builders still have to reckon with.