By the Banks of The River Ilissos
ΣΤΙΣ ΟΧΘΕΣ ΤΟΥ ΠΟΤΑΜΟΥ ΙΛΙΣΣΟΥ

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The River Ilissos (Ιλισός or Ιλισσός or Ειλισσός) is one of the two rivers of Athens, first known from signs of 5th c. BC. It drains the western slopes of Mt. Hymettos, and originates from several converging seasonal creeks. 

As urban Athens expanded in the 19th and, even further, in early 20th centuries, the river became a source of pollution and was gradually converted into a rainwater runoff conduit, covered with streets that track its original, twisting route, along the lay of the land. 

The River Ilissos flows under Mesogeion Avenue at the Old Gendarmerie Academy, runs under Michalakopoulou (now in the modern-day suburb of Ilissia) and Vassileos Constantinou Avenues, and passes in front of the  Panathinaiko Olympic Stadium, where it was bridged in the 19th c. ​​The river used to flow along the fortification walls of Athens. Its banks -in the busy intersection that today features the Hilton Hotel and the National Gallery- were grassy and shaded by plane trees, and were considered idyllic in antiquity. The temple of Pankrátēs, a local hero, was located there, giving its name to the modern suburb of Pangrati. 

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By Hera! What a fine place for rest! How large and tall this platanus tree is! And, this chestnut tree, how magnificent is its shade and majestic its branches! These places are all in bloom and balmy. A delicious spring ripples at the roots of this platanus and by dipping our feet we may feel the coolness if its waters. To judge by these figurines and statues one might say that this abode is consecrated to Nymphs and to the Acheloos river. How the air that we breathe here is sweet and agreeable! It is like the perfume of Summer, harmonious with the chorus of grasshoppers. But, what I like best, is this soft turf, thick enough to rest our heads comfortably, stretching ourselves on this gently inclined ground. My dear Phaedros, thou could have not lead me to a better place!

Plato, Phaedros

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​In the ancient times, Ilissos was considered to be a sacred river. It was believed that the Nine Muses used to live on its banks and there was a sanctuary named "the Altar of the Ilissiads".  Ilisos was also a semi-god, the son of  Poseidon and Demetra, and was worshiped in a sanctuary on the Ardittos Hill, next to the current Panathinaiko Olympic Stadium. This area was called Cynosarges in antiquity, and the spring of  Kallirrhóē was located there.  Among the many legends and stories that are supposed to have taken place by the banks of Ilissos, this is where King Kodros sacrificed himself to save Athens from the invading Dorians. Ilissos River then flows to the southeastern flank of the ruined Temple of Olympian Zeus, where it is still visible amidst reed beds, next to the Christian church of Agia Foteini "of Ilissos". As is the case for the majority of the Christian churches in Greece, Agia Foteini, was built in 1872 on the ruins of an ancient temple, dedicated to Hecate.

Τhe 5th B.C ionic temple of Artemis (Diana) Agrotera on Ardittou Street, by the banks of River Ilissos, as seen by J. Stuart and N. Revett in 1808, then altered and with additions, now in ruins.

New 2014 archaeological finds identify the ruins of yet one more 4th c. BC temple, dedicated to Zeus, "Μειλίχιον Δία", in the vicinity of that of the 5th BC ionic temple of Artemis (Diana) Agrotera, a bit higher up on the same slope of the hill, which is thought to have been called "Agrai". It was here that the illustrious goddess was celebrated every year on the anniversary of the Battle of Marathon. The Archon in charge would offer goats for sacrifice and the tithe of the sale of war prisoners, while the Athenian youth passed in procession. The importance of this hill was due to the Lesser Mysteries, celebrated every year in the month of Anthesterion (February-March) as a form of initiation of the Great Eleusinian Mysteries. The Hill of Agrai goes as far as the Stadion and is known under the name of Ardettos or Helicon. Here the visitor may also discover the Shrine of the God Pan. This rocky outcrop with a small natural cave and two perpendicular faces was found to carry a relief of the god Pan. This deity of the wild nature was regularly worshiped in caves and rocky terrain. Pan is depicted striding to the right with the "pipes of Pan" in his right hand and a stick for hunting hare on the left. Others believe that this is the Shrine of the Nymphs and the river god Acheloos, with a spring of cold water, a plane tree and a willow, where, as Plato writes, Socrates and Phaedros sat during their philosophical chats. Ilissos then flows under Thesseos Avenue, in the suburb of  Kallithea, its original course turning sharply northwest to join the Kifissos River, of which it was once a tributary. The Ilissos is now routed straight to sea, coming to surface and running into the Saronic Gulf in the middle of Faleron Bay.

The ancient spring of Kallirrhóē by Simone Pomardi, 1820.

"Athens from the Ilissos", by G. N. Wright, 1842.

1919 Ilissos by Fred Boissonas

In this old photograph, left to right: The Philopappos Monument, the Weiler building which now houses the administration for the Acropolis Museum, the Acropolis, the ruins of the Temple of Olympian Zeus and closer to us the banks of the River Ilissos and the building that was built over the Temple of Agrotera Artemis.

In older times the river at this point would expand into shallow marshland, called "Vatrachonisi" ("Frog Island") in the vicinity of the ancient spring of Kallirrhóē, now submerged under Kallirois Avenue.