Copais

Lake Copais in ancient literature and mythology

There was a legend that the lake came into being when the hero Heracles flooded the area by digging out a river, the Cephissus, which poured into the basin. Polyaenus explains that he did this because he was fighting the Minyans of Orchomenus: they were dangerous horseback fighters, and Heracles dug the lake in order to unhorse them. Another story has the lake overflow in the mythical time of Ogyges, resulting in the Ogygian deluge.