The player enters on the top level of a two-level circular penthouse that occupies the entire top of the Lucky 38 tower. If Mr. House is still alive, Victor stands next to the elevator, and the player will find Jane, a friendly robot who will talk about Mr. House and will offer to buy snowglobes from the player for 2000 caps each.
Down the stairs to the left on the lower level is a terminal with a large display screen where the player can communicate with Mr. House, if he is still alive, or Yes Man, if his personality has been installed into the mainframe during Wild Card: Change in Management.
To the left of the large terminal and tucked behind a staircase is a terminal on the wall with a hard lock. This terminal opens the secret door to Mr. House's inner sanctum, allowing access to an elevator to the control room, where the actual Mr. House can be found. The terminal can also be unlocked with the access codes, which the player gets by obtaining either a Lucky 38 VIP keycard or the platinum chip. Opening the door via the terminal will immediately turn the securitrons hostile and fail The House Always Wins, if that quest is active.
There are some other miscellaneous rooms and furniture, including safe storage containers and a bed the player can sleep in.
If the player kills Mr. House, Jane will no longer be there, which removes the option of selling snowglobes. The achievement can still be unlocked, as the player just needs to collect all seven to get the achievement, but the snowglobes will not leave the inventory and cannot be placed on the stand in the Lucky 38 presidential suite.
Almost everything in the Lucky 38 is marked "unowned" and can be taken with no Karma penalty.
If you fly above the Penthouse with console commandtcl, you will see a door, that can't be accessed. In G.E.C.K. this door is referred to as "HouseInnerSecretDoor".
There are three protectrons in a room in the penthouse. They seem to be just statues, and one of them is a Nuka-Cola security protectron.
When demonstrating the Mark II software upgrade to the player during the quest The House Always Wins, Mr. House states that the grenade launcher upgrade is part of the Mark II software. However, if the player becomes hostile to the penthouse securitrons, they will use grenade launchers against the Courier even if the player has not yet provided the platinum chip containing said upgrade to Mr. House.