The Peiros is a river in the central and the northwestern parts of Achaea, Greece. The river is known locally under several names including Kamenitsa. he Peiros is the longest river in Achaea. It rises in the northeastern part of the Erymanthos mountains, near the village Lakkomata. It passes through the municipal units of Farres, Olenia and Dymi. It flows into the Gulf of Patras between the towns Alissos and Kato Achaia.