Lab (Luigi's Mansion: Dark Moon)
From the Super Mario Wiki
The Lab is a room in Gloomy Manor in Luigi's Mansion: Dark Moon. The Lab was first shown during the opening cutscene, where the shattering of the Dark Moon caused the Greenies to go ballistic. This room can be accessed by either one taking the bottom door on the west wall of the Common Hall or by dropping down to it via the fireplace in the Parlor. Inside the Lab, there are several red machines that were in use by E. Gadd before he had to leave due to the Greenies causing trouble.
During Gear Up, Luigi must go into this room to find a Slammer that has taken a gear from the mechanism in the Foyer. In Visual Tricks, Luigi needs to go to the Lab to retrieve the Dark-Light Device that Professor E. Gadd left. He must enter via the fireplace as the door to the Lab from the Common Hall will disappear because of Spirit Balls released by the Boo. In Sticky Situation, the Lab may be one of the rooms covered in spider webs.