Basement (Luigi's Mansion 3)

Basement is an area in Luigi's Mansion 3. It is located below the Grand Lobby. The area contains a laundry room and parking garage, as well as Professor E. Gadd's lab. Luigi first explores this area near the start of the game, when he falls through the laundry chute after being chased by King Boo down the hallway of RIP Suites. He falls into the laundry room and is awoken by Polterpup, who leads him to the parking garage where he finds a red vehicle with the Poltergust G-00 inside. Polterpup then teaches Luigi how to use the vacuum, as well as the Strobulb and Burst. Luigi is then able to walk up to the first floor of The Last Resort.

Luigi returns to the basement later on after rescuing Professor E. Gadd. The professor sets up his portable laboratory and gives Luigi the Virtual Boo, allowing them to communicate at any time. He then sends Luigi on a mission to get his briefcase from the fifth floor. When Luigi returns with the briefcase, Professor E. Gadd opens it to reveal a capsule with a green goo-like substance which he injects into the Poltergust G-00. He then teaches Luigi how to use Gooigi. Luigi can return to Professor E. Gadd's lab at any time to play ScareScraper mode, view collected ghosts and gems in the vault, and talk to the professor.

Rooms

 * Laundry Room
 * Service Hallway
 * Garage
 * Service Stairwell
 * Elevator Shaft

Gem locations
There are 6 square gems in Basement 1. Luigi cannot get every gem until after he has gotten the Poltergust G-00 and the Dark-Light Device, has learned the Suction Shot, and has teamed up with Gooigi.
 * Diamond: Found in the trunk of the hooded car in the parking garage. Luigi must use the Poltergust G-00 to suck up the tarp, then flash the green light with the Strobulb to pop open the trunk.
 * Ruby: Found in the caged area at the far left of the parking garage. Gooigi must walk through the chain-link fence, pop open the electrical box with the Suction Shot, then flash the green light to access the gem.
 * Sapphire: Found in the hidden elevator shaft to the far right of the parking garage. The player must use the Suction Shot to pull off the metal cover, then enter the tunnel. Luigi must climb the ladder to the top of the shaft, then have Gooigi drop down through the grate and get the gem.
 * Emerald: Found in the middle dryer in the laundry room. Luigi must use the Suction Shot to pull the cover off the dryer.
 * Amethyst: Found in the hallway outside the parking garage. Luigi must use the Dark-Light Device on the painting near the garage door.
 * Citrine: Found near the top of the stairs right before the Grand Lobby. Gooigi must ooze through the bars on the floor to get to a platform with the gem.