The Three Marys caverns are located along the river past the Three Marys map marker, in the first area with three large rocks, and consist of a cave with two entrances. The first entrance is on a ledge on the southern bank of the river, but can be accessed from the northern bank via a rock bridge.
Going through the cavern and then using the other entrance provides a shortcut past the westernmost bend of the river. There are three White Legs pain makers inside, and sleeping facilities. In the canyon, the ground is heavily littered with trash and debris.
- Three Marys cavern will not show up on the player character's compass, nor can it be discovered as a fast travel location until Crush the White Legs has been started. The latter is due to the main path through the canyon being permanently blocked during the quest, requiring the cave to be used to bypass the rocks when re-visiting Zion later.
- If the area is visited before Crush the White Legs, the early portions of the valley are lightly guarded, but no White Legs can be found deep inside the area where it looks as if it should be heavily populated, despite it apparently being their base of operations in the Zion Valley.
- If the area is explored before the final quest, the path at the end will be blocked by a rock. Using console commands to pass the blockage will reveal the final area where Joshua and the player character confront Salt-Upon-Wounds at the end of the questline, however, it will be empty at the time.
- White Legs storm-drummers can be observed target shooting at empty bottles and tin cans at several points throughout Three Marys if the player character remains undetected.
Behind the scenes
- Question: "Why is Three Marys so full of garbage? The White Legs didn't haul all kinds of pre-war junk they're clueless about (electronic doodads, coffee makers, microscopes,) from SLC, did they?"
Joshua Sawyer: "They both haul around junk and litter with the stuff they go through."
(Josh Sawyer Formspring answers)