The Valens Aqueduct (Turkish: Bozdoğan Kemeri, meaning “Aqueduct of the grey falcon”; Greek: Άγωγός του ὔδατος, Agōgós tou hýdatos, meaning simply “aqueduct“) was the major water-providing system of medieval Constantinople (modern Istanbul, in Turkey). Restored by several Ottoman Sultans, it is one of the most important landmarks of the city.
The aqueduct stands in Istanbul, in the quarter of Fatih, and spans the valley between the hills occupied today by the Istanbul University and the Fatih Mosque. The surviving section is 921 meters long, about 50 meters less than the original length. The Atatürk Bulvarı boulevard passes under its arches.
Today it is usually called the Aqueduct of Valens, since it was finished in 368, during Valens’s reign, but there is reason to assume that it was already planned and begun in Constantine’s time.39 As mentioned above, the aqueduct runs parallel to one of the streets in the old part of Byzantium. Also, its southeastern
prolongation would exactly meet the main entrance of the courtyard in the Great Palace that is now the Mosaic Museum. It is obvious that the aqueduct was planned in a clear relationship to the street system of the old town of Byzantium. Arches 26/27 and 52 are wider than the others in the aqueduct and were certainly
intended to serve as passages for streets.40 At other points where we would expect similar wider arches, the original construction is lost, for example, at the northwestern end close to the church of the Holy Apostles, where the aqueduct was completely rebuilt in Ottoman times.
The construction of a water supply system for the city (then still called Byzantium) had begun already under the Roman emperor Hadrian. Under Constantine I, when the city was rebuilt and increased in size, the system needed to be greatly expanded to meet the needs of the rapidly growing population.
The Valens aqueduct, which originally got its water from the slopes of the hills between Kağıthane and the Sea of Marmara, was merely one of the terminal points of this new wide system of aqueducts and canals – which eventually reached over 250 kilometers in total length, the longest such system of Antiquity – that stretched throughout the hill-country of Thrace and provided the capital with water. Once in the city, the water was stored in three open reservoirs and over a hundred underground cisterns, such as the Basilica Cistern, with a total capacity of over 1 million cubic meters.
“Aqueduct of Valens (in the City)” (Istanbul) engraved by J.C.Bentley after a picture by W.H.Bartlett, published in The Beauties of the Bosphorus, 1838. Steel engraved print with recent hand colour. Good condition. Size 18 x 14.5 cms including title, plus margins. Ref G3331
The exact date that construction on the aqueduct began is uncertain, but it was completed in the year 368 during the reign of Roman Emperor Valens, whose name it bears. It lay along the valley between the third and fourth hills of Constantinople, occupied respectively at that time by the Capitolium and the Church of the Holy Apostles. According to tradition, the aqueduct was built using the stones of the walls of Chalcedon, pulled down as punishment in 366 after the revolt of Procopius. The structure was inaugurated in the year 373 by the urban prefect Klearchos, who commissioned a Nymphaeum Maius in the Forum of Theodosius, that was supplied with water from the aqueduct.a[›]
East Roman (Byzantine) period
Other works were executed under Theodosius II, who decided to distribute the water of the aqueduct exclusively to the Nymphaeum, the Baths of Zeuxippus and the Great Palace of Constantinople. The aqueduct, possibly damaged by an earthquake, was restored under Emperor Justinian I, who connected it with the Cistern of the Basilica of Illusb[›] (identified today either with the Yerebatan or with the Binbirdirek (Turkish: Turkish): “thousand and one columns”) cistern, and was repaired in 576 by Justin II, who built a separate pipe.
The aqueduct was cut by the Avars during the siege of 626, and the water supply was reestablished only after the great drought of 758 by Emperor Constantine V. The Emperor had the whole water supply system repaired by a certain Patrikios, who used a large labour force coming from the whole of Greece and Anatolia.
The last Byzantine Emperor who took care of the aqueduct was Andronikos I Komnenos. Neither during the Latin Empire nor during the Palaiologan period were any repair works executed, but by that time the population of the city had shrunk to about 40,000 – 50,000 inhabitants, so that the water supply was no longer a very important issue. Nevertheless, according to Ruy Gonzáles de Clavijo, a Castilian diplomat who traveled to Constantinople en route to an embassy to Timur in 1403, the aqueduct was still functioning.
After the Fall of Constantinople (1453), Sultan Mehmet II repaired the whole water supply, which was then used to bring water to the imperial palaces of Eski Sarayi (the first palace, built on the third hill) and Topkapı Sarayi, and connected it with a new line coming from the northeast. The great earthquake of 1509 destroyed the arches near the Mosque of Şehzade, which was erected some time later. This gave rise to the popular legend that they were cut, in order to allow a better view from the nearby mosque. The repairs to the water-supplying net continued under Beyazid II, who added a new line.
Around the middle of the 16th century, Suleyman I rebuilt arches (now ogival) 47 up to 51 (counted from the west) near the Şehzade Mosque, and commissioned the Imperial Architect Sinan to add two more lines, coming from the Forest of Belgrade (Belgrad Ormanı). The increased flow allowed the distribution of water to the Kιrkçeşme (“Forty Fountains”) quarter, situated along the aqueduct on the Golden Horn side, and so called after the many fountains built there under Suleyman.
Under Sultan Mustafa II, five arches (41-45) were restored, respecting the ancient form. An inscription in situ, dated 1696/97, commemorates the event. His successor Ahmed III repaired again the distribution net.
The Aqueduct of Valens had a length of 971 meters and a maximum height of ca. 29 meters (63 meters above sea level) with a constant slope of 1:1000. Arches 1-40 and 46-51 belong to the time of Valens, arches 41-45 to Mustafa II, and those between 52 and 56 to Suleyman I. Arches 18-73 have a double order, the others a single order.
Originally the structure ran perfectly straight, but during the construction of the Fatih Mosque – for unknown reasons – it was bent in that section. The masonry is not regular, and uses a combination of ashlar blocks and bricks. The first row of arches is built with well-squared stone blocks, the upper row is built with four to seven courses of stones alternated with a bed of smaller material (opus caementitium) clamped with iron cramps. The width of the aqueduct varies from 7.75 meters to 8.24 meters. The pillars are 3.70 meters thick, and the arches of the lower order are four meters wide.
The water comes from two lines from the northeast and one coming from the northwest, which join together outside the walls, near the Adrianople Gate (Edirne Kapı). Near the east end of the aqueduct there is a distribution plant, and another lies near Hagia Sophia. The water feeds the zone of the imperial palace. The daily discharge in the 1950s amounted to 6,120 cubic meters. During Byzantine times, two roads important for the topography of medieval Constantinople crossed under the eastern section of the aqueduct.
CISTERN of AETIOS
This open cistern in the northwest of the city was built in 421 and filled with water from the supply line leading to the Aqueduct of Valens. In the middle byzantine time, it was probably already used as a garden.