The above YouTube video by ChristosNYC is of a former hospital on Roosevelt Island which I must assume is the former smallpox hospital but which could be of another ruin since demoslished as noted below.
Currently the access to the ruin is under tighter restrictions due to injuries sustained by two RIOC PSD officers who were chasing unauthorized intruders. In other words do not attempt to dupliacte the images on this video.
Per the videographer:
"abstract exploration of now demolished ruin of abandoned Victorian style hospital on Roosevelt Island in New York City's East River. Shot as part of Graduate Film program work in the early 1990s. "