Kewu Plain, also known as Prambanan Plain or Opak River valley, is a fertile volcanic plain that lies between Merapi-Merbabu complex in the north, Bantul lowlands and Sewu karst limestone range in the south, Bengawan Solo river valley in east, and the Progo River in the west, and Kedu Plain on northwest. It is located within the Yogyakarta Special Region, Sleman Regency, Klaten Regency and Solo City (Central Java).