Sentinel Site

Sentinel Site Prescott, marked in the game as just Sentinel Site, is a location found in the Glowing Sea in 2287.

The facility is one of the few places in the Glowing Sea that is hardened against radiation, so the player can safely remove whatever gear they are using to prevent radiation damage while inside.

Background
An ominous pyramid surrounded by irradiated sludge, Sentinel site Prescott was officially a nuclear munitions disposal facility. However, in reality it was a missile silo that stockpiled Mark 28 nuclear warheads for the U.S. military, and performed experiments focused on combining them with existing ballistic missiles.

With a seemingly inexhaustible stock of these warheads, they performed at least 23 test launches, the final one performed on the eve of the Great War. The launch failed to register with the system, locking the hapless staff inside and dooming them to death of hunger and thirst. Many were turned into feral ghouls, sealed beneath the ground. Captain Dunleavy of the 132nd Engineering Corps operating the site recorded the final moments of the crew before the first MIRVs hit the Commonwealth and he realized that the Great War happened.

By 2281, the site was penetrated by the Children of Atom, who were able to activate the launch sequence before being massacred by the feral ghoul inhabitants. Although no missile was present on the launch pad, all internal blast doors in the facility were closed and locked, requiring the Sole Survivor to deactivate the sequence in order to gain full access to the facility. The sole survivor retreated deeper into the facility with his Assaultron, seeking to protect the holy stockpile of Mark 28s from blasphemers and apostates. The Brotherhood of Steel followed later, seeking to provide Liberty Prime with a new supply of nuclear weapons, straight from Prescott's silos.

Layout
The exterior of the structure is a concrete pyramid, with a large blast door entrance on the north side. As the Sole Survivor enters the facility, they will find themselves in a rather tall room that looks like a missile silo with some catwalks going through it. In the first control room when you go left after first entering the site, go in, and down the stairs to the right is a Sentinel site blast door override holotape on the teal control panels, it will open the blast doors in the facility.

At the bottom of the facility, there are three unused nuclear warheads in metal crates and a fourth on a forklift. They will not detonate from gunfire or explosions but be prepared for a horde of feral ghouls hiding in a tunnel nearby. At the end of the tunnel there is an elevator that will take the Sole Survivor to a second exit; not marked on the map. When the elevator is called, a leveled glowing one will appear guarding a crate with minor loot.

The rest of the tunnel continues down further to a cargo bay; there is a cargo elevator that leads up to a secondary entrance is off to the side, but straight ahead is a control room containing Brother Henri and Atom's Wrath if Liberty Reprimed is active. The terminal in this room requires Henri's password to open and is able to open the locked red door in the loading dock, which is an expansive room filled with nuclear warheads; the room contains moderate to severe radiation, peaking at 28 rads per second near the back of the room.

Notable loot

 * Astoundingly Awesome Tales issue #19 - Found in the first control room when walking left from entering the site (lower half of room to the right of the bottom of stairs on the teal control panels).
 * Sentinel site blast door override - Found in the same room as the Astoundingly Awesome Tales on a different desk. Two more copies can be found inside the two terminals behind the blast doors.
 * Three Vault-Tec lunchboxes can be found here:
 * One in the lower tunnels, inside a hidden tiny room accessible via a hole in the left wall of a large room you pass through. The hole in question has ghouls crawl out of it when you enter.
 * One in the flooded room in the lower levels, behind the nuke on the righthand side (immediately before ending elevator).
 * One under a bunk in a barrack room on the lower levels.
 * Captain Dunleavy's holotape - On a desk in the console room with Brother Henri and Atom's Wrath, near the large stockpile of nukes (the room is only available after the relevant quest has started).
 * A mini nuke - At the end of the lower levels in the room with the Mk. 28 nuclear bombs in a knocked over crate, right next to the objective to place the signal pulser.
 * Henri's terminal password - Carried by Brother Henri, gives access to his terminal.
 * Henri's instructions - A note also carried by Brother Henri.

Related quests

 * Liberty Reprimed

Appearances
The Sentinel site appears only in Fallout 4.

Behind the scenes

 * The exterior design of the Sentinel site mimics that of the real-world Stanley R. Mickelsen Safeguard Complex, the anti-ballistic missile radar and missile installation pyramid near Grand Forks, North Dakota. The facility was built as part of the Safeguard anti-ballistic missile program, itself a scaled-back version of a previous program dubbed Sentinel.
 * The original Sentinel Program was designed to place nuclear-tipped interceptor missiles in the suburbs around major cities, protecting them from incoming ballistic inbound threats. The project was scrapped due to public backlash, but one site was partially constructed near Sharpner's Pond in North Andover, MA.
 * In the real world, the Mk-28 nuclear bomb (also known as B28) was the longest-serving US tactical nuclear weapon, commissioned in 1958 and retired only in 1991. Some versions of this weapon were actually used as missile warheads, however not on ICBMs.