Worth the Deep Journey A large island in southeast Asia, Borneo features beautiful peaks and rich rainforests that offer dynamic experiences to travelers. The island itself is part of three different countries. Much of Borneo belongs to Indonesia, while the north side is mostly part of Malaysia. Inset in the northern coast is the nation of Brunei, about the size of Delaware. Areas in the interior of Borneo can be hard to navigate as the network of rivers diminishes, making such places retain their natural beauty.