The Customs House is the tenth chapter of Drake's Fortune. Along their way to the harbor, Nate and Elena ventured through the customs house to find a way to the escape boat in the harbor.
Story[]
Sic Parvis Magna[]
Logbook entry featuring El Dorado.
Shortly after reuniting, Nate and Elena entered a room that contained all of the old ship manifests. After taking a brief look around, Nate approached a nearby table to study a logbook he suddenly spotted. It contained information about the Esperanza, which sailed from Callao, Peru, carrying a gold statue weighing 20 arrobas (500 pounds). Upon turning the page, Nate found a detailed drawing of El Dorado, which unfortunately happened to be the last entry in the book.
Watching Nate fiddle with his necklace, Elena asked if it was from "somebody special". He explained to her that it belonged to Francis Drake and that he inherited it. Elena then read its inscriptions: Francis Drake's motto, "Sic Parvis Magna" (Greatness from Small Beginnings), along with the date it was made, the 29th of January 1596, the day after Sir Francis supposedly died. Beside these were coordinates to the burial site off the coast of Panama, left as a clue by Sir Francis. Nate then tore the El Dorado page out of the log, held it up to the camera screen, and stated that it was the closest to El Dorado that they were getting.
Harbor View[]
Nate and Elena stand over the balcony, searching for the boat.
The two continued through the building, where they soon found themselves in another gunfight with several of Eddy Raja's pirates. Once the way was clear, they approached a balcony, and from there, they saw no sign of the boat until Nate spotted it on the far side of the building's dock. Elena suggested that he go alone, and swing back around to pick her up, that she could capture more footage of the island. Nate went ahead and crossed the balcony, shortly before entering into a large, domed building where he found himself trapped.
Walkthrough[]
Nate and Elena take cover from Mac.
Once you and Elena reunite, head up the stairs and proceed forward to the ship manifest room. Following the cutscene, head up the stairs and prepare for another gunfight, starting with a big pirate wielding a Moss - 12. This particular shootout can be difficult, as the only exit out of the room is covered by a pair of pirates on a staircase, another group on the left, another one high up on a platform, and another one on the second staircase around the corner, wielding an M79. Although it is possible to make it up the first staircase for the superior position on the second floor, it leaves your rear entirely exposed, and thus it is too much trouble to go for.
Nate fights pirates from the balconies.
As such, maintain your position at the doorway and take down as many pirates as you can from there, then the one on top of the platform (if he will likely shoot past your cover), and then shoot down the remainder. After that, head to the staircase and use the winch to open the gate to the right. After the cutscene, shoot the lock off the door, then jump across to the balcony, which will begin to crumble and slope downwards. When Nate is sent sliding, quickly tap 
as prompted to have him leap to the next balcony.
You will then need to shoot down a few more pirates that attack you from inside the building. As you leap across the gaps in the balcony, you will soon approach a real large one, with a broken door sitting right across from it, right at the edge. You will need to shoot its lock off to break it apart, then make a precise jump over the gap. Pass through the door to enter the large building, where the next chapter begins.