The river has its sources on Mount Olgassys, and in its northwestern course formed the boundary between Paphlagonia and Bithynia. It empties itself into the Euxine (Black Sea) about 90 stadia west of Amastris.
Mount Olgassys serves as the river's source, and as it flows northwest, it forms the boundary between Paphlagonia and Bithynia. The river ultimately empties into the Euxine (Black Sea) about 90 stadia west of Amastris.