Rather than a clearly defined geographical term, "Northern Epirus" is largely a political and diplomatic term applied to those areas partly populated by ethnic Greeks that were incorporated into the newly independent Albanian state in 1913. The term "Northern Epirus" was first used in official Greek correspondence in 1886, to describe the northern parts of the Janina Vilayet. According to the 20th century definition, Northern Epirus stretches from the Ceraunian Mountains north of Himara southward to the Greek border, and from the Ionian coast to Lake Prespa. Some of the cities and towns of the region are: Himarë, Sarandë, Delvinë, Gjirokastër, Korçë, and the once prosperous town of Moscopole. The region defined as Northern Epirus thus stretches further east than classical Epirus, and includes parts of the historical region Macedonia. Northern Epirus is rugged, characterized by steep limestone ridges that parallel the Ionian coast, with deep valleys between them. The main rivers of the area are: Vjosë/Aoos (, Aoos) its tributary the Drino (, Drinos), the Osum ( Apsos) and the Devoll ( Eordaikos).