Borneo is a location in Uncharted 2: Among Thieves; it is the third largest island in the world and is located to the north of Australia. Its landscape is largely jungle. While north Borneo is Malaysian, the rest of the island is Indonesian.
In the 13th Century, Marco Polo and his fleet of 13 ships were shipwrecked on the island.
In Uncharted 2: Among Thieves, Nathan Drake arrives at Borneo to search for clues of where the Cintamani Stone could be. He is accompanied by Victor Sullivan and Chloe Frazer. Also in Borneo is Zoran Lazarevic, who is searching for Polo's lost fleet. After infiltrating Lazarevic's camp, Drake soon realises that Polo must have fled to high ground, to avoid a tsunami. They discover an underground temple, filled with dead bodies and blue resin, as well as the Phurba Dagger.
In the non-canon mission Nate, Sully and Chloe infiltrate Lazarevic's camp to discover what are in Draza's crates. After collecting the four pieces of the Janus head, having killed Draza, they travel to London.
Located high up in a mountain, the caverns were last occupied by Marco Polo's crew, who had drank the resin.
During "The Dig," after searching through Marco Polo's journals, Nathan Drake realized that they had to head to higher ground. Higher up, Drake, Sully, and Chloe discovered some fairly small underground caverns. They found blue resin, which they used to light the way, and the Phurba dagger inside.
The caverns consist of three main rooms. One is the largest, which is littered with blood and human skeletons. The second is filled with barrels that contain blue resin. The third is concealed behind a damaged wall and contained the Phurba.