The Vault - Fallout Wiki

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The Vault - Fallout Wiki
Mass Fusion Building
Fo4 Mass Fusion Building.png
Worldmap Loc Img 184.png
Map MarkerMass Fusion Building
Mass Fusion Executive Suite
FactionsMass Fusion (formerly)
QuestsMass Fusion (quest)
Spoils of War
Cell NameMassFusionExt
MassFusion01 (interior)
MassFusion02Trans (elevator)
MassFusion02 (main reactor)
ref id0000e05a
000f4bf4 (interior)
0014fc9b (elevator)
00084a59 (main reactor)
TerminalsMass Fusion Building terminals:
Executive Research Lab Terminal
Product Development Terminal
Development Manager's Terminal
Mainframe Control Terminal
Records Terminal
Reception Terminal
Customer Service Terminal
Security Office Terminal
Prototype Lab Terminal
Attendant's Terminal
Reactor Security Control
Analyst's Terminal
Facilities Terminal
Reactor Control Terminal
Intern's Terminal

Mass Fusion Building is a location in the Commonwealth.


The largest skyscraper in Boston belonged to the pre-War Mass Fusion corporation, which made a fortune by supplying power to Boston and most of the Commonwealth. This headquarters for the corporation was constructed with the proceeds from an enormously lucrative line of fusion wells, engines, and cores. Since the war, the structure has fallen into disrepair, and although the Gunners fight in the streets below, the reactor level hasn't yet been breached.[1]


Lower levels

The main lobby has several defense posts set up by the Gunners. Several offices line the walls, including the security office in the northeast corner which has an elevator that goes down to the basement. Staircases on the eastern wall of the lobby leads up to the second floor, a hallway lined with more offices.

A bridge leads to the other side of the floor which contains an office with a collapsed roof, leading up to a balcony on the third floor offices. A busted wall leads out to the central lobby and another collapsed roof up to the fourth level. Another collapsed roof leads to the fifth floor which is the last one able to be accessed, but a noticeable hole in the roof against the northern wall is present which is access point from the higher levels to the lower levels.


Accessed from the elevator in the security office of the ground floor, the basement contains the Mass Fusion reactor. From the entrance, there is a room off to the side, which holds some Protectron pods and a prototype lab terminal. On the opposite side is a staircase down to the control room of the reactor. The reactor itself is accessed through a doorway on the southeast side of this room, and is dangerous radioactive, peaking at 98 rads per second on the bottom of the reactor. Catwalks lead up to the reactor's control terminal at the top, where the radiation peaks at 188 rads per second.

Upper levels

The upper levels are only accessible during Spoils of War or Mass Fusion. A room rests on top of the roof, with entrances on the southern, eastern and northern walls. An elevator (requiring a Mass Fusion executive ID to activate) sits in the center of the room; a staircase off to the side leads up to the executive research lab, while the elevator leads down the side of the building into the lower levels.

The elevator stops at the eighth floor. Several offices line the walls, with a room containing an armor workbench and weapons workbench in the southern room. This room also contains a collapsed roof that leads to the ninth floor which is dominated by several terminals and switchboards.

Notable loot

  • The Strength bobblehead is found atop the statue on the fifth floor that overlooks the main lobby; the statue is just above the globe statue in the middle of the ground floor.
  • The "Giant Super Weapons" issue Tesla Science Magazine is found on a console in the southeast corner of the ninth floor.
  • Beryllium agitator, in the Muss Fusion reactor core in the basement. This item is only accessible during Spoils of War and Mass Fusion.
  • Freefall Legs armor pieces, in an office in the northeast corner of the interior office hall, a jetpack must be used to reach the office.
  • Jack Rockford's log in the Intern's Terminal in said hard to reach office.
  • Fusion core in an office niche in the northwest corner of the interior office hall. A jetpack must be used to access this.
  • The Mass Fusion executive lab password is found in a desk on the second floor of the building on the roof.
  • The Mass Fusion executive ID is found in the same desk as the Mass Fusion executive lab password.
  • Oslow's office recording can be found be found on a table in the executive research lab on the roof.
  • The Mass Fusion labs key is found in the northwest room on the fourth story after descending from the rooftop lab down the elevator.


  • When this building was constructed some of the floors were not connected by stairwells.[2]


The Mass Fusion building appears only in Fallout 4.


  1. Fallout 4 Vault Dweller's Survival Guide Collector's Edition p.477-479: "[15.01] MASS FUSION BUILDING
    Before the war, Mass Fusion was the primary power supplier to Boston and most of the Commonwealth. It is the tallest building in Boston. With the proceeds from an enormously lucrative line of fusion wells, engines, and cores, this structure—their corporate headquarters—was built. Since the war, the structure has fallen into disrepair, though the reactor level hasn’t yet been breached.
    At ground level, Gunners fight through the rubble-strewn streets. Should you arrive on the roof (when the quest is active), prepare to fight your chosen rival faction, and hunt down a few choice items (including a Nuka Cherry). Beware the oil, gas leaks, and explosive barrels, or use them to your advantage."
    (Fallout 4 Vault Dweller's Survival Guide Map)
  2. Jack Rockford's log, 09-17-77