Elevator Hall (Hotel Shops)
From the Super Mario Wiki
The Elevator Hall is a location in Luigi's Mansion 3. It is found on the first floor of the Hotel Shops on the third floor of The Last Resort. It is east of the Mall Lobby and west of the Restroom. The white Gem can be found here.
There are rotating doors in the southwest corner of the elevator hall which lead to the main lobby. To the left are plants with Bills hidden in them. Luigi can pull off the tarp in the northeast corner to reveal a treasure chest behind bars that Gooigi can get to. There are more bills in the light fixture. Luigi can pull off the picture of nail pools to the left of the women's restroom to get more bills. To the right of the men's restroom, underneath the painting of a ghost is a bin with coins. The restrooms are to the right. The women's restroom is out of order, so Luigi is only able to access the men's restroom. There is a shelf near the restrooms with a telephone on it. There is another telephone Luigi can use the Dark-Light Device to reveal. He can then use the telephone to reveal a Golden Goob.