The Maintenance Building is a structure and location in the MarbleHornets series. It is a dilapidated building with lots of debris and large rusted machines that look like ventilation devices. Inside, there are a lot of tubes, corroded wall paint, and rust everywhere. It is also underground without windows because it is always dark. As of Entry #58, it appears to be the maintenance shack of the second hospital building.
So far the room has appeared five times: in Entry #22, Entry #23, Entry #58, and Entry #60. In Entry #22 the tape shows Alex and Seth a cameraman who appears sparingly in the old tapes and wandering a ruined building for unknown reasons. Audio distortions happen during the entire tape, and visual distortions happen rapidly. Seth is grabbed and yanked off camera as the footage distorts into madness with no proper audio and a deformed face appears in the frazzled static. When the tape cuts back in, Alex is inside of what is assumed someone else's house, and is talking about how Seth is gone. Alex states that he doesn't know where Seth is being unable to find him, and that Seth, Brian, Sarah, and Jay are all gone. He can't remember anything that happened at all.
In Entry #23, Jay is wandering through Brian's house and stumbles upon the building somehow. He wanders it momentarily, looking for the source of a calm deep voice, only to be assaulted by The Operator personally for the first time and the camera and audio fail. When he wakes up at his apartment he finds the camera completely ruined, and the tape all that's left.
Entry #58 finally gives a precise location: the maintenance building of the burned out hospital. Jay is led there by Hoody (whom he is chasing) and finds multiple pump machines and various objects. There appears to be a maintenance tunnel in the building which may lead to the room where Seth was attacked, but Jay is forced to turn back as Tim is aggravated and neither man has a flashlight.
In Entry #60, Jay goes into the tunnel found in the building. While searching, he hears footsteps in the building above him (most likely Hoody). After searching the maze of tunnels, he finds several of Tim's medical documents, as well as the Operator doll from Brian's house, both of which he takes with him. Very soon after the Operator appears and chases him out of the tunnel. Somehow Jay manages to escape, but has the memory loss that comes with encounters from the Operator. He claims that he never wants to return to the tunnel again; so far, there have been no more visits to the building.