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Valens Aqueducts

“It should also be observed that none of those who have the right to use the water shall be subjected to any expense for repairs, as it would be abominable for the inhabitants of this Beautiful City to be compelled to purchase water.”

Codex Justinianus 11.42.7 (from the reigns of Emperors Theodosius and Valentinian)

The Aqueduct of Valens (Greek Ἀγωγὸς τοῦ ὕδατος) stretched across the valley east of the Church of the Holy Apostles between the Fourth and Third Hills of Constantinople. It dates to the late 4th century and was again used in the Ottoman era, when it was known as Bozdoğan Kemeri (“Aqueduct of the Grey Falcon”). The Aqueduct of Valens is not merely a bridge of arches, but an immense network that supplied Constantinople water for many centuries.

While it has been commonly argued that it was built in the early 2nd century by Hadrian, it is now generally accepted that it was first completed by Valens (364-378). It is possible it was first initiated by Constantius II (337-361). It included a long-distance line that eventually brought water from over 120 kilometers away in Thrace on more than 250 kilometers of channels. The orator Themistius praised Valens for welcoming the Thracian nymphs to Byzantium. This water supply system was probably completed when the monumental Nymphaeum Maius was built in the Forum of Theodosius by the Prefect of Constantinople Klearchos in 372-373. Thus it was completed around five years before Valens’ defeat by the Goths at the Battle of Adrianople, which opened Thrace to enemy attack. The Long Walls of Thrace were built during the reign of Anastasius (491-518) partly to protect this long-distance water supply system. Halkalı, a main aquiferous area about 15 kilometers west of Constantinople, also supplied this aqueduct system.

The Aqueduct of Valens was necessary as many new parts of Constantine’s new city had a higher elevation than Byzantium and its older aqueduct system built by Hadrian (117-138). As Constantinople’s water supply lines were extensively redeveloped by the Ottomans, it is difficult to determine the surviving Roman and Byzantine features of the system. However certain geographical features and archaeological remains allow for a hypothetical course to be proposed. The elevation of this water supply line suggests that the Valen’s line originated at Halkalı and entered the city north of the Gate of Charisius (Edirnekapı). This line had a higher elevation that supplied the open cisterns of Aetius and Aspar, crossed the Aqueduct of Valens, and terminated in the Cistern of Philoxenos. Several channels were discovered within the city walls that have approximately the same elevation, including channels at the fora of Constantine and Theodosius.

The aqueduct system was repeatedly restored during the Byzantine era. It was restored by Justin II (565-578) after it was damaged by an earthquake. The Valens line was cut by the Avars during the Siege of Constantinople in 626, and was only restored in 758 by Constantine V (741-775). It is unclear, though, how serious the damage was. While it has generally been argued that the Valens line ceased functioning completely, it also has been suggested that the city continued to be supplied by water sources closer to the city, such as Halkalı. In other words, it is possible the Avars mainly damaged the long-distance line coming from Thrace. The long-distance water system was probably beyond repair by the 12th century, so the city possibly mostly relied on the water sources from the Belgrade Forest, as it did later during the Ottoman era. It seems that the waters of Halkalı continued to supply the Aqueduct of Valens during this period. Following the Latin conquest of Constantinople in 1204 it is likely that the water supply system no longer functioned and the city had to rely on rainwater water collected and stored in cisterns.

Mehmet II ordered work on the aqueduct system to supply shortly after the conquest of Constantinople in 1453.  It seems that the ruins of Byzantine aqueducts were still prominent when he began to rebuild the water systems, making it unclear how much was restored or rebuilt. It included work on the Halkalı system, which was supplied by the Beylik system and included a monumental aqueduct Mazulkemer. While it has often been dated to the Roman or Byzantine eras, recent surveys suggest Mazulkemer probably dates to the reign of Mehmet II. The Süleymaniye system, which also used the Halkalı system, was built during the reign of Suleiman the Magnificent additions to supply Süleymaniye Mosque. This system could supply 1000 cubic meters of water per day. While the Beylik system only used Mazulkemer, the Süleymaniye system also passed over Avasköy and Ali Pasha aqueducts. Sultan Mustafa II (1695-1703) also restored the Aqueduct of Valens (Bozdoğan Kemeri), while his successor Ahmed III (1703-1730) restored the Halkalı water supply lines.


Architecture of the Aqueduct

The Aqueduct of Valens is a bridge of arches that originally began around the Church of the Holy Apostles and terminated at a large nymphaeum in the Forum of Theodosius. Its total length is now 971 meters with a maximum height around 28 meters. It has a total of 86 arches. It is a single-story structure for the first 15 arches on the western side. Much of the aqueduct has a thickness of 5.65 meters. The ruined section of the aqueduct is around 335 meters. Originally the aqueduct continued in the direction of Fatih Mosque. The structure was built of limestone blocks, though later restorations during the Byzantine era altered the structure, for example adding brick arches. Repairs also took place during the reigns of sultans Beyazıt II, Suleiman the Magnificent and Ahmed III. It seems that an earthquake in 1509 caused the section of the upper tier around Şahzade Mosque to collapse and another section further east to be totally destroyed.


Christogram on the aqueduct


Inscription of Sultan Mustafa II

Records repairs on the Aqueduct of Valens


Aerial photo by Kadir Kir

Solidus of Valens 

Dumbarton Oaks

Valens or Valentinian I

Galleria degli Uffizi, Florence

Carole Raddato

From the “Orations of Themistius”

Blessed, happy Constantine! Do you sense that for you the emperor (Valens) has turned the beloved from an inanimate to an animate state, and that against expectation he has breathed life into this beautiful and desirable body that was still feeble, to say it with Homer, and that for you the city is truly a city and no longer a mere sketch? You and your son were clever in finding for her and giving to her many and manifold girdles and necklaces and bracelets and torques. And lest bedecked with much gold and precious objects she be more thirsty than those who are dressed in rags, you would have made great expenditure, but this honour was preserved and left to another, since God took care that the thank-offering of the emperor did not appear second to the imperial garb, which the beautiful city had first fixed on him. Now both exchange rivalling gifts with one another and not gold for bronze but things of quite equal worth. And it is difficult to pronounce which of them is more precious. For famous and renowned poets agree with both, one calling the imperial rank godlike and the other declaring water the best thing. But the originator of both of you rejoices and revels in this rivalry. I hear that he enquires with joy about the number of the nymphs and the course in order that with you as a leader and guide they appear from here and there and are invited to the Bosphorus. And the names are Thracian and manly, but the beauty and the splendour are exceedingly delicate. And one is tempted to call Pirene and Thisbe mere chatter and that Alphius troubled himself in vain when loving Arethusa. And I did not see winged Victories and Amores in bronze or in stone or in colours, but God let grow wings on the emperor's virtues alone. Thus they come to us faster than thought and neither rocks hold them back nor narrows nor the tops of high mountains nor craggy cliffs nor lightless ravines, but they run underneath the ones and around the others and they fly high above the third and they have come together into one place and have welcomed each other and have made a pact to flow together to the temple that is Constantine's by name but is already Valens' as far as its construction is concerned. For by right the origin of each thing does not belong to the one who started it but to the one who completed it. You, however, have both begun the headpiece of good fortune for it and completed it. And before, as it seems, it did not deserve its name and when we used the epithet 'rich' it was idle words. But since your expenditure and your love of honour have called the nymphs inside and have settled them inside, they are not only rich but are already thrice rich. (XI.151a-152b)

For the city of Constantine and of the son of Constantine, with whose blood you have been mixed and the race of founders is already immortal and secure for us through the blood that you share with them, this city was in a certain sense beautiful even before and did not shame the love of the founders but with all their zeal and eagerness both lovers ended up seeing it beautiful rather than making it so. It was as if somebody fell in love with a beautiful and noble woman and took care of rouge and makeup and cosmetics and other things (so that very many of them appeared on her) and by Jove also of precious bracelets and earrings and purple and gilded dresses, and dressed her up once with these and then again with others and applied makeup to her and brought things together from every land and sea, but saw her afflicted by thirst and drought and not far from vanishing together with the gold and together with the purple. From such a love the beloved has indeed great profit! But your uncle who as I believe divined that you would wed the city, instead of making a mere sketch strove to inscribe the name of Constantine on an adamantine pillar and he made her the mother of imperial rank and soon gave the city clouds, which he took from Zeus out of heaven, having gathered as maidservants in one place these, which were situated here and there far apart from each other and which squatted in unpleasant and useless haunts. And they, faster than wings and thought, either fly high up through the air or run underneath steep jutting hills, in the earth and in the air, resembling a bunch of grapes as regards their backs, more than a thousand stadia uphill and downhill, neither running upwards nor downwards, and neither being held down nor being held in. And roofed over they come together and they have arrived here before the gates and they camp in the open waiting for the originator in order that with him as host they might settle in their temple, in which dance together Hephaestus and Asclepius and Panacea. (XIII.167c-168c)

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Drawings by W.H. Bartlett (1838)

From Chronicle of Theophanes Confessor

There ensued a drought, such that even dew did not fall from heaven and water entirely disappeared from the City. Cisterns and baths were put out of commission; even those springs that in former times had gushed continuously now failed. On seeing this, the emperor set about restoring Valentinian's [Valens] aqueduct, which had functioned until Herakleios and had been destroyed by the Avars. He collected artisans from different places and brought from Asia and Pontos 1,000 masons and 200 plasterers, from Hellas and the islands 500 clay-workers, and from Thrace itself 5,000 labourers and 200 brickmakers. He set taskmasters over them including one of the patricians. When the work had thus been completed, water flowed into the City.


Ottoman Aqueducts of the Halkalı System



Mazulkemer (“dismissed from office” aqueduct) is the first aqueduct of the Halkalı system. It has commonly been dated to the Roman and Byzantine eras, though recent surveys suggest it was likely built during the reign of Mehmet II. It is around 110 meters long and crosses Uzuncaova Stream. It is made of calcareous stone and has two tiers of arches, with 13 arches on the upper tier and 7 on the lower tier. Some of these arches are in ruins, while others show several phases of modification. The remains of three levels of terracotta pipes were also found in the aqueduct.


Ali Pasha Aqueduct


Avasköy Aqueduct

Istanbul Archaeological Museums


Statuette torso of Aphrodite

Saraçhane (near Aqueduct of Valens)

From bath? Roman era?


Bull’s head

Probably from the Baths of Constantine  

Found near the Aqueduct of Valens

5th-6th century


The Water Supply of Byzantine Constantinople by Crow, Bardill & Baylis

The Longest Roman Water Supply Line by Kâzım Çeçen

Two Romes: Rome and Constantinople in Late Antiquity edited by Lucy Grig and Gavin Kelly

Fountains and Water Culture in Byzantium edited by Brooke Shilling and Paul Stephenson

Bildlexikon zur Topographie Istanbuls: Byzantion, Konstantinupolis, Istanbul bis zum Beginn d. 17. Jh by Wolfgang Müller-Wiener

İstanbul'da Bizans Dönemi Sarnıçlarının Mimari Özellikleri ve Kentin Tarihsel Topografyasındaki Dağılımı by Kerim Altuğ

Oxford Dictionary of Byzantium edited by Alexander Kazhdan

“The infrastructure of a Great City: Earth, Walls and Water in Late antique Constantinople” by James Crow

“The water supply of Constantinople: Archaeology and Hydrogeology of an Early Medieval City” by P. Bono, J. Crow, and R. Bayliss

“The Water Supply of Constantinople” by Cyril Mango

“Water-supply infrastructure of Byzantine Constantinople” by K. Ward, J. Crow, and M. Crapper


Orations by Themistius edited by Schenkl & Downey

The Code of Justinian translated by S.P. Scott

The Chronicle of Theophanes Confessor translated by Cyril Mango and Roger Scott


Aqueduct of Valens Photo Album (Byzantine Legacy Flickr)

Water Supply (Nicholas V. Artamonoff Collection)

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