The fortress is a location in Drake's Fortune, appearing in "The Fortress", "Unlocking the Past", and "Out of the Frying Pan". It is located on the former Spanish colony, where it was once built by the Spanish, and after their disappearance had once served as a working place for Francis Drake. During Drake's Fortune, it was occupied by Eddy Raja and his pirate crew.
In "The Fortress", Nate stumbled upon the massive fort while trekking through the island in search of Elena Fisher, whose parachute he had spotted hanging in a tower, while in the wreck of the Hog Wild. He climbed several walls and fought through numerous of Eddy Raja's pirates as he navigated through the location. He eventually managed to make it to her parachute, at which point he spotted Elena herself through a window in the distance, which prompted him to continue his search through the fort.
In "Unlocking the Past", Nate found a room that contained a map of the island and a message written on a wall left by Francis Drake. It read, "Fletcher - we have gone to the great tower. I pray that you'll meet us there. Francis Drake". Following this, Nate made his way up to Drake's tower, which he had spotted outside. Though there was still no sign of Elena, Nate discovered Drake's old telescope and used it to take a peek at the shipwrecks that were still in the harbor. Immediately thereafter, he saw Elena down below, who was about to get shot by one of Eddy's men.
After Nate saved her he was himself attacked and knocked unconscious, ending up in a jail cell, where he was ultimately found by Elena herself. Elena used knowledge of a previous episode of her show that the bars only needed a good tug to be removed. While she was working on Nate's prison break, Nate encountered his former business associate Eddy Raja. After a small confrontation between Nate and Eddy, in which Eddy offered for Nate to join him in a chance for freedom, Elena managed to bust Nate out using a jeep. The two fled from Eddy and his men during "Out of the Frying Pan", through the jungle, eventually reaching the flooded city.
The fortress is a large, coastal defensive structure made primarily out of a mix of white and grey bricks, constructed on the cliff-tops of the southern corner of the bay, where it meets the ocean. The entire area has largely fallen into a state of disrepair, with many structures having collapsed, either fully or partially. Numerous plants freely grow in and on the fort, such as the vines on the walls, or the large white jungle trees dotted throughout the many courtyards and on-top of the incredibly thick walls. Many rooms inside the fortress itself remain intact, often containing numerous crates, and were apparently used for storage.
The initial wall that Nate scaled stands on the southern side of the island, featuring a series of barred windows that belong to a long corridor, largely empty except for stacks of crates. The corridor runs along the entire southern wall and connects to three small yards on the inner side. Said yards are connected by gated archways, but only the second and third remained accessible in this manner. The third courtyard was larger, also featuring a staircase to the roof where Nate found Elena's parachute, and it had another archway that led to the flooded chambers underneath the keep in the center of the fort.
Underneath the keep was a large and expansive chamber, containing numerous support pillars for the keep above-ground. The pirates have added their own walkways to two of the pillars, and also used four spaced out gaps near the ceiling on two opposite walls, presumably connected to the keep itself, to ambush Nate. The floor is covered with a shallow layer of water, and with barely any light sources present, it gives the area a heavy blue-tone. The chamber connects to a separate smaller room that could be flooded with the use of two winches, with another passage leading further up through the keep itself, exiting outside in another courtyard.
The northern side of the fortress features another set of two courtyards, one of which features a tall, stone, cylindrical tower also featured on Francis Drake's map. The tower was located near the north-east of the fortress, on top of the wall. Nearby the tower is a winch that opens a gate to a connected plaza, in which stood a formerly locked door that leads to a corridor, containing three cells. Nate was temporarily locked up in the central jail until Elena removed the wall using a jeep. Both the plaza and the jail corridor connect to the largest courtyard on the northern side.
Said courtyard has a long rectangle shape, featuring numerous smaller rooms on both sides. On the left was a staircase leading to a long passage on-top of the wall, that trailed all the way along up to the larger room on-top of the front gate. It was here that Drake carved his map and message on the wall. The room has another exit leading to the roof on the east side of the courtyard, from where he originally spotted the tower Drake mentioned in his message. The path to the tower itself has largely collapsed, as it was only accessible by traversing a series of ledges high up through the broken structural remains of the northern side. The tower itself gave a good view of the nearby bay, being able to overlook much of the island, with the flooded city visible in the distance.