The Terrace is one of the final areas of the Treacherous Mansion.

When Luigi came in E-2 "Double Trouble" or E-3 "A Train to Catch", it had nothing in it, however when E-5 "Paranormal Chaos", Luigi had to inspect the terrace, finding King Boo opening the paranormal portal, sending all ghost out the mansion, after Luigi clears all exhibits, kitchen and the toilets he needs to go back to the terrace and suck the rest of the ghosts. After clearing these missions, Luigi will return in the Boss mission: Stop the Knightmare, being warped, also, if you look closely, Mario's painting can be seen here in the boss mission


King boo opening the paranormal portal