The treasure vault is a location that appears in Drake's Fortune. It is located on the hidden island once belonging to the Spaniards, and it is a large labyrinth in which the Spaniards hid El Dorado, located underneath the monastery. It was initially discovered by Francis Drake, who died there, and later actually emptied by the Nazis, who connected it to their bunker. The descendants appeared to have made their home close to it, as it was where they first appeared en masse in the open.
In "Sanctuary?", Nathan Drake and Elena Fisher, rescued Victor Sullivan and discovered he still had Francis Drake's diary. Sully explained that the Spanish marked their secret vaults with a symbol of two keys diagonally pierced through the Sacred Heart symbol and that they only had to find the symbol to find the vault, and thus the treasure. After some time spent going through the monastery, during "On the Trail of the Treasure", Sully radioed Nate and mentioned a possible hidden gallery at the monastery's church.
Upon returning to the building Nate discovered a stained glass window depicting the Sacred Heart, and after solving a puzzle, discovered the gallery. Here, he found another stained glass window, that when opened allowed a clear view of a large mausoleum, with the same symbol on its roof. After luring Gabriel Roman and Atoq Navarro away from the location, and killing several of Atoq Navarro's mercenaries, Nate gained entry to the mausoleum and met up with Elena and Sully. After solving another of the Spanish' puzzles, they discovered a hidden passage, although only Nate and Elena were able to go through.
In "The Treasure Vault". Nate and Elena explored the vault, while Sully stayed behind. By following the clues Francis Drake left on his map, the three Roman numerals II, V, and VII, they were able to find their way through the maze, with Nate twice sighting a humanoid creature watching him in the distance. In the second half they were confronted by Eddy Raja and his gang of pirates. After fighting through them, the two eventually reached the heart of the vault, in the namesake chapter "The Heart of the Vault", where they found Francis Drake's corpse. Nate, dismayed with the realization that Drake never did find the treasure and just died there, left his heirloom ring at Drake's remains.
While Elena searched for a way out of the vault, Nate encountered Eddy and Prakoso running from the descendants, who soon began swarming the room, quickly killing Prakoso. Eddy himself fell shortly after, after an intense firefight, with him and Drake trying to fight them off. With Elena's help, Nate was rescued from death by the descendants, and they both managed to escape the creatures and make their way out of the vault, escaping through a thick door into the nazi bunker.
The vault is a large labyrinth divided into two caverns, separated by a large wall. Placed throughout the area are Roman numerals engraved into plates, placed on the ground and walls. They range from I to VII, and appear to exist solely as a visual aid for visitors who know the right numbers to follow.
The layout of the vault is intentionally set out as a vertical and horizontal maze, with numerous classical arched bridges, staircases, and other paths seemingly placed at random throughout the chambers. The Roman numerals will indicate most of the paths, but some appear to have collapsed over time, or lead to other blocked off areas, or seemingly into no passage at all.
The first cavern is accessed through a hidden tunnel accessed from the largest mausoleum in the monastery's graveyard. It immediately opens into a grand view of the entire chamber, with direct access to a locked gate to the second chamber, past a small center area. Said center area has some sort of small marker placed in the center, holding up a series of flags, likely indicative of the descendants who have placed similar markers around the area. Numerous paths are available from this path, but most are either dead ends or inaccessible, with numerous grates blocking off access to side rooms. A plaque with a V led to a waterwheel mechanism atop a stone bridge, which when rolled into place activated a series of contraptions.
The main activated devices were huge swinging lanterns, which were also lit on fire. Said lanterns served as a deterrent, and obfuscated part of the path that lead to a wooden elevator, to the right of the main gate. Said elevator, which Nate managed to reach and lower both by accident, raised a barred, metal window set inside the main wall, through which he reached the second cavern.
The second area does not contain any traps, but is much larger than the first, featuring more wooden bridges and walkways, as well as massive wooden stairs spiraling around stone towers, which itself acted as support pillars for the roof. The gate between the two chambers was again accidentally raised by Nate, through lowering another wooden elevator, which also lowered a nearby drawbridge.
The presence of Eddy Raja and his pirates proves that there were additional passages leading into the vault from the outside, although most still appeared to be closed off. There was a deliberate winch-and-ladder contraption, which led to a wooden walkway and spiraling staircase, which itself connected to a wooden platform and large staircase high up near the ceiling. In the distance, numerous other towers, bridges, and walkways are visible, but not reachable. The staircase led to another tower, with another wooden path around the size that allowed access to the heart of the vault.
The heart of the vault
The so-called heart of the vault, located towards the very top of the location, is where the treasure was hidden, with only the corpse of Francis Drake remaining. It is a large round chamber, entirely empty save for some rubble and debris. A second-floor walkway spans the entire room, being held up by stone support pillars placed a small distance from the walls, forming another circle. There are several gaps in the floor, all near the walls, through which the descendants gained access to the room. At the second floor walkway is another passage, connecting to a Nazi bunker control room.