The Abandoned Hospital is a major focal point of the MarbleHornets ARE. It clearly has some connection to The Operator and his activities, and is repeatedly visited by Alex and the rest of the cast. Throughout most of the ARE, it is only assumed it is some form of hospital, however Tim reveals in Entry #66 that it is actually a mental hospital.
One of the earliest times it is visited is in Entry #51, where Brian is being brought there by Alex.
In Entry #66, Tim explains that he was a patient there and that he had had horrid hallucinations which he now believes were most likely visits from The Operator. He also mentions at one point it did indeed burn down, so the structural damage of the building was fire damage. During the entry, Tim and Jay both see Hoody here.
Jay and Tim have not made any visits to this building since. Based on what Jay and Tim have said to each other, they are both reluctant to do so.
It is possible that the fire damage to the building was caused by The Operator, since he appears to be able to maipulate fire, as seen at Jay's Apartment.
As one can see, most of the building is in deep neglect, clear been unoccupied for a long time
Excessive paint damage is prevalent everywhere in the building. The person in this photo is Brian.
Rubble, dust, and debris litter virtually every room. Some of it is sediment, other parts have fallen fixtures or metal.
Tim was found in a room in Entry #52
Tim in Entry 66 talking to Jay. Apparently the room they're standing in was his room.
The back corner of this room has a DVR tape. Whether Hoody left it or not is uncertain, but it proves Jay and Tim aren't the only ones coming to this building every so often.
Written on the wall and found by Jay. Jay later finds medical records in the nearby Maintenance building, so it most likely insinuated Tim had been lying to him up until this point.
The double doors on the right sent Tim into a state of extreme panic.