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 common 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 channel than ran from more than 250 kilometers. 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 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 (AD 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 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 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. The elevation of this water supply line suggests that the Valen’s line originated at Halkalı and entered the city north of 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.
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 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 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 Magnificient 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
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.
Drawings by W.H. Bartlett (1838)
Ottoman Aqueduct 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
Statuette torso of Aphrodite
Saraçhane (near Aqueduct of Valens)
From bath? Roman era?
Probably from the Baths of Constantine
Found near the Aqueduct of Valens
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