The Harbormaster Hotel is a very small area consisting of the main hotel lobby, room 61 on the sixth floor (all of the other rooms are blocked off), and the hotel roof, guarded by some raiders.
After taking the elevator from the lobby, opposite the exit on the sixth floor is an Advanced-locked door. Behind this door is an unusual scene: the skeleton of someone sitting in a chair holding an overdue book, while surrounded by a Giddyup Buttercup wearing a bowler hat and "smoking" a cigar, a Jangles the Moon Monkey wearing a sea captain's hat, and a teddy bear holding a baby rattle while inside of a plastic pumpkin perched on top of an overturned trash can.
The Harbormaster Hotel appears only in Fallout 4.
Behind the scenes
The Harbormaster Hotel is based on the real-world location of the Boston Harbor Hotel located on Rowe's Wharf, geographically similar to the in-game equivalent.
Several items in the lobby on a small table and on the front counter (including clean glasses, a glass pitcher, a clean coffee cup, an undamaged camera, a preserved Fancy Lads Snack Cakes, an unused ashtray, and a preserved cigarette pack) are all incorrectly marked as owned; taking the items is thus considered to be stealing.[verified]