The construction of a water supply system for the city of
Byzantium began under the Emperor
Hadrian.
Constantine the Great re-founded the city and greatly expanded it which meant that demand for fresh water greatly increased. The Valens aqueduct, which originally sourced 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 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 combined capacity of over one million cubic metres. The water comes from two lines from the north-east and one coming from the north-west, 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 . According to tradition, the aqueduct bridge was built using the stones of the walls of
Chalcedon, pulled down as punishment in 366 after the
revolt of
Procopius. According to
Themistius, the first phase of the aqueduct's construction was 1,000
stadia in length – . Together, these three cisterns could hold approximately of water.
Middle Byzantine period The aqueduct was cut by the
Avars during the
siege of 626; the supply was only reestablished after the great drought of 758 by the Emperor
Constantine V (). In 1075, the official in charge of the aqueduct's maintenance was
Basil Maleses, the
protovestes and former judge recorded by the Greek historian
Michael Attaleiates as having been captured by
Alp Arslan's
Seljuks at the
Battle of Manzikert. After the
First Crusade's passage through Constantinople, both
William of Malmesbury and
Odo of Deuil mentioned the working Aqueduct of Valens in their histories. William of Malmesbury claimed that the
Danube's water was carried into the city by hidden channels and washed the dirt from Constantinople, while Odo of Deuil stated that "from the outside conduits flow in, bringing the city an abundance of water". At this time, the city was the largest in Christian Europe, its population sustained by the water supply.
Late Byzantine period Andronikos I Komnenos was the last Byzantine emperor who maintained the aqueduct. It was not maintained during the
Latin Empire nor during the
Palaiologan period. 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.
Ottoman period After the
fall of Constantinople (1453) the
Ottoman sultan,
Mehmed the Conqueror (), repaired the system. The water was then used to supply the imperial palaces of Eski Saray
(Old Palace) and
Topkapı Sarayı. The system was enhanced by a new connection 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 network continued under
Bayezid II (), who added a new line. Around the middle of the 16th century,
Suleiman the Magnificent () rebuilt arches (now
ogival) 47 up to 51 (counted from the west) near the Şehzade Mosque, and commissioned the imperial architect,
Mimar 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
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. In 1912, a part of the aqueduct near the Fatih Mosque was pulled down. In the same period, a new modern
Taksim ("distribution plant",
lit. 'division') at the east end was erected. ==
Bozdoğan Kemeri ==