Achelous is the second longest river in Greece. It begins in the Pindus Mountains and after flowing south for 220 kilometers, it empties into the Ionian Sea. The river carries 200 times more water in winter than in summer and is prone to destructive floods. Its upper course was home to pastoralists and bandits, while its lower course, despite flowing through fertile valleys and plains has never attracted a large settled population that would establish prosperous cities. Near the river’s mouth, there were marshes that proved detrimental to permanent settlement, while siltation blocked access from the sea to the only important ancient Greek city established on the river’s shores, Oiniadai.