ILISSOS

The 'Ilissos' or 'Ilissus' was a river in ancient Greece. Now it has been largely canalised into undeground routes.
During antiquity it ran outside Athens' defensive walls. The only section of it still visible in modern times is a small area to the south of the Temple of Olympian Zeus. Ilissos was also a demi-god, the son of Poseidon and Demetra, and was worshipped in a sanctuary on the Ardittos Hill next to the current Panathinaiko Stadium.