Poseidon Reservoir

The Poseidon Reservoir is a location in the Commonwealth in Fallout 4.

Layout
Poseidon Energy Reservoir not only distributed water to the surrounding farmlands and towns, but it was also a source of hydroelectric power. The power generated was used by Poseidon for its research facilities scattered about the Commonwealth. Currently, the reservoir is in a state of disrepair. The hydroelectric generators no longer operate and the water has become stagnant.

The roof gantries are easy to access, and the ferals up here can be wiped out while you gaze south at Natick and Lake Cochituate. Inside, the terminal in the first metal office pod opens the security doors leading deeper into the facility. The Poseidon Reservoir Safe Key is on top of the metal pod, near a locked toolbox (Expert): at the top of the metal walkways, jump to the left and over the pipe. In the back left is the toolbox and the key.

Notable loot

 * Robot model kit parts in a Railroad stash (indicated by the "sun"-symbol) accessible via a brown pipe going into the lake, accessible via an underwater breach in the pipe, outside next to the factory.
 * Master safe in the foggy lower level to the southeast, behind some large tanks.

Quests
Cleansing the Commonwealth
 * Learning Curve - This is one the locations where you need to escort a scribe of the Brotherhood.

Appearances
The Poseidon Reservoir only appears in Fallout 4.