Papua New Guinea occupies the eastern half of the island of New Guinea, just north of Australia, and many outlying islands. The Indonesian province of West Papua (Irian Jaya) is to the west. To the north and east are the islands of Manus, New Britain, New Ireland, and Bougainville, all part of Papua New Guinea. About one-tenth larger than California, its mountainous interior has only recently been explored. Two major rivers, the Sepik and the Fly, are navigable for shallow-draft vessels. Constitutional monarchy with parliamentary democracy.