The Lounge is a room in the Haunted Towers in Luigi's Mansion: Dark Moon.
The Lounge is shown as a heavily damaged room with only a few tiles remaining where the only way to reach the Lounge is with the Balloon Berry Luigi uses in the Laboratories. Spiky vines are shown on the ceiling which are there to pop Luigi's Balloon Berry, there are a couple of cream colored armchairs hanging off the edges of the destroyed tiles and a crack in the wall that looking through it shows the inside of the Conservatory, the door to the left enters the Water Supply.
The Lounge is the second to last room Luigi reaches in B-1 A Job For A Plumber, where Luigi gets to the Lounge to reach the Water Supply using the Balloon Berry to get up to the door. In B-2 and B-3 the Lounge can be entered again the same way with the Balloon Berry in the Laboratories but is entirely for show other than the way to get the gem in the Laboratories if the player hasn't already. in B-4 and B-5 the Lounge cannot be accessed because of the door to the Laboratories in the Skybridge is blocked off by vines, and in Hostile Intrusion it can be entered just like most of the rooms but serves no purpose but to get the earlier mentioned gem.