The Kahayan river, or Great Dyak, is the largest river in Central Kalimantan. The provincial capital Palangka Raya lies on the river. The main inhabitants are Dyaks, who practice slash-and-burn rice cultivation and pan for gold on the upper reaches. The lower Kayahan flows through a rich and unusual environment of peat swamp forests, which has been severely degraded by an unsuccessful program to convert a large part of the area into rice paddies, compounded by legal and illegal forestry.