 It flows west through a deep valley, between the mountains Parnassos and Kirphe, passing south of Delphi, through the Delphic Landscape and the plain of Amphissa and flows into the Corinthian Gulf near Kirra.The water of the Castalian Spring flow into Pleistos.Solon of Athens is said to have used hellebore roots to poison the water in an aqueduct leading from the River Pleistos around 590 BC during the siege of Kirrha.