It is right next to Swan's Pond. It can be used to get into Vault 114. It used to be a subway station until some time before the Great War, when its ownership was transferred from the Boston MTA to Vault-Tec. Vault-Tec used the station as an entrance to their newly constructed Vault 114, which was exclusive to Boston's upper class citizens. Once inside the vault, the residents were subjects in a social experiment which would place them in very harsh and deprived conditions.
(Note: This area contains both the station itself and the unfinished area behind the Vault 114 door that the tunnel ends at. Vault 114 does not technically begin until entering the next area past the large room with the construction equipment in it.)
The entrance leads down an escalator and into the first room, where there are several Triggermen to handle. There are a few odds and ends worth looting here, some of which are behind a Novice locked door in the storeroom behind the counter. In the same storeroom there is also a floor safe with an expert lock on it. A sleeping bag and a mattress can be used on this level.
Going down to the next level will lead to the subway tunnels. The staircase is trapped with a makeshift bomb. A bed can be found in a room on the southeastern side of the area. The first tunnel area has a Novice locked door on the left side back wall, and the hall behind it contains an Expert locked safe as well as a tripwire triggering a pipe pistol trap and a sleeping bag. The next tunnel area has a door on the far wall on the left which leads to a manhole exit to the outside area above Vault 114. At the end of the tunnel, the right tracks dead-end at some rubble, and the left tracks lead to the Vault door.
Through the Vault door, there is a room with a bunch of Vault-Tec boxes and a terminal with the information about this Vault and a "social experiment" that was to be done here. Past this is a large unfinished room with construction equipment and more Triggermen. At the far end is a small room with the entrance to Vault 114.
- Overdue book - In the first room, on the double bench on the far wall, opposite the entryway where the escalator out to the Commonwealth is.
- Nuka-Cola Quantum - At the end of the track running along the right side of the first tunnel area, held by a skeleton lying in a pile of rubble.
- Vault-Tec lunchbox - In the same area as the Nuka-Cola Quantum but diagonally opposite, on the ground next to the other tunnel opening (located at the corner of a large blue crate, just to the right of two small red and one white Vault-Tec boxes).
- Vault-Tec lunchbox - At the end of the tunnel where the Vault 114 door is located, on the opposite side of the tracks from the vault door, on the floor between an overturned cigarette machine and the wall.
When Codsworth is near the vault door, he will sometimes exclaim "A Vault?! Down here?!
Park Street station appears only in Fallout 4.