Alpheus (ălfēˈəs) [key] or Alfiós älfēôsˈ, river, c.70 mi (110 km) long, rising in the Taygetus Mts., S Greece. The longest river in the Peloponnesus, it flows northwest through gorges, past Olympia, and onto the Olympia plains before entering the Ionian Sea. In Greek mythology, its waters were said to pass under the sea and to emerge at Syracuse (Italy) in the fountain of Arethusa. Hercules, to clean the stables of Augeas, turned the Alpheus through them. It is the river Alph of Coleridge's poem Kubla Khan. The lower Alpheus was formerly known as Rouphia.