The Hospital is near the abandoned building in Rosswood Park. It plays a role in the filming of Marble Hornets. It was used as Brian's old, burnt down school. Tim seems to have a personal connection to it.
Below are the videos that feature the abandoned Hospital.
Alex and Tim walk into the hospital while scouting for locations and examining possible film sites. Tim, at various intervals, has mild coughing fits. Alex does not like any of the locations given and is asking Tim to move all over the hospital. Tim then excuses himself for a moment, and accidentally leaves his camera pointed backwards. Tim walks behind a wall, and begins talking to Alex. Alex then picks up a stick and attacks Tim behind the wall, and Tim goes silent. The camera falls down, and The Operator is standing nearby. There is heavy distortion, then The Operator disappears. Alex walks in front of the camera, holding the stick, then he walks off camera. Tim is then heard coughing.
Tim and Jay visit Rosswood. Tim wants to show Jay the hospital but Jay insists on looking at the abandoned building. He sees the hooded man and tries to follow him.
Jay returns to the abandoned hospital alone. While exploring the maintenance tunnel the Hooded Man led him to in Entry 58, Jay finds a folder containing some of Tim's old medical records near a slender doll. Jay then encounters the Operator in the tunnel and quickly leaves, taking the doll and the records with him.
Entry #65 chronicles Tim's point of view complementary to Entry #64. He runs through Rosswood and drives to the abandoned hospital, where he seems to be psychologically tortured by the Operator. He makes Jay agree to visit the hospital.
After Tim and Jay meet up and agree to come back to the hospital, Entry #66 chronicles the events that happen there. Tim tells Jay about his connection to the hospital, saying that he was a patient there ever since he was a kid, that he used to hallucinate a figure whose identity he couldn't remember, and had schizophrenia (his Masky persona). Tim wonders if the thing he was hallucinating was actually the Operator, that it wasn't an illusion, and has a nervous breakdown. Eventually Jay catches a glimpse of the hooded man walking around the hospital, and decides to follow him, Tim bringing a pipe with him. The hooded man walks into a room, after walking out, Jay searches the room and finds the hospital tape. After a few more minutes of tailing him, Jay and Tim are led outside the hospital and into a field, with no sign of the hooded man anywhere. Tim gets angry, having no idea as to where he went, and he and Jay walk away.