|Fallout 4 created by Bethesda Game Studios.|
Images used for educational purposes only.
- The Poseidon Reservoir is located in the southwest of the Commonwealth, a little ways south of Fort Hagen and just beyond an eastbound highway. You should be on the edges of the Glowing Sea when you come across the Poseidon Reservoir. Though it’s possible you’ll find the thing on your own, you’re more likely to come here when sent by Knight Rhys as part of a Cleansing the Commonwealth operation. The quest Last Voyage of the U.S.S. Constitution can also bring you here, depending on your Intelligence stat.
- The Poseidon Reservoir is a den of Feral Ghouls, and on approach you’ll find lots of them waiting around the entrance. There aren’t many places to hide ‘round here, so expect a brutal firefight unless you’re really sneaky. The front entrance is right beside the road.
- Have a look at the outside of the place first, after clearing the front. There are stairs on the north side of the building which you can use to climb to the roof. There are more Ghouls up here, guarding a maintenance room with an Armor Workbench. A pair of double doors up here lead to the highest point of the Reservoir, though aside from a 10mm Automatic Pistol all you’ll find up here is a nice view of some lit buildings to the south. Meh.
- You’re almost done with the outdoors. Head to the north side of the Reservoir and you’ll see a long, brown pipe extending into the lake. There’s a hole in the side of this pipe, just barely sticking out of the water, that you can enter to climb into a small, secret niche of the Reservoir. Along with some ammo you’ll find Robot Model Kit Parts. Yay, a toy!
- Return to the main entrance and pop inside. Unless you’re ready for a scrap, be very quiet upon entering. There are a number of Ghouls lurking on the catwalks near the front door, and if one of them gets wind of you, all of them will rush and pin you. The first room on your right contains an Armor Workbench, some minor items and a terminal that can deactivate a nearby security door. Do this, as there’s no other way through the door.
- Head upstairs to start. Aside from Ghouls there’s very little up here until you reach the very end of the path, where you’ll find several Ghoul corpses. Look to your left and down and you’ll see a toolbox on a nearby girder. Hop off of the catwalk, unlock the tool box if you want, and then hop over the brown pipe next to it. There’s a tool case back here, and sitting beside it, rather well hidden, is the Poseidon Reservoir Safe Key.
- Return to ground level, take a left, and head downstairs. There are Ghouls in the room ahead, along with a Weapons Workbench, and yet more Ghouls lurking beneath the entrance catwalk on your right. Crafting tools abound, and not much else.
- The security door you opened above is in the southeast of the bottom floor, through the maze of pipes and girders. There’s a bathroom on your right through the hall with some medical supplies. Beyond are stairs, and there’s a Glowing One at the bottom, along with one other Ghoul. (The Glowing One is your target for Rhys, if applicable.) Keep your distance from this thing and try to take its legs out before it can drive you into the previous room - it’s a pain to kill among the supports.
- Basement! Time for your rewards. In the northeast corner of this jammed, flooded room is a Chemistry Station, a steamer trunk filled with goodies (Including a Poseidon Radar Transmitter for Last Voyage of the U.S.S. Constitution), and a Master locked safe with more of the same, assuming you can get it open. You know, with that Safe Key you found earlier. Done!