The Terrace is one of the final areas found in the Treacherous Mansion of Luigi's Mansion 2. It can be reached during multiple missions, even if it's only necessary going here during the events of E-5.
When Luigi first checks the room in E-2: Double Trouble or E-3: A Train to Catch, there's nothing in it. However, in E-5 "Paranormal Chaos", Luigi has to inspect the room, and founds King Boo opening a paranormal portal, that will send all different type of ghosts out in the mansion. After Luigi clears all exhibits, kitchen and toilets, he needs to go back to the terrace and suck the rest of the ghosts. In E-Boss: Stop the Knightmare, Luigi will return here and will be warped by the portal in a paranormal area, where the last Possessor Ghost is attending him.
- If you look closely during the mission E-Boss, Mario's painting can be seen in this room.