‘The city thirsts’

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Water in Istanbul: past, present, and future

Supplying Constantinople with water was a monumental challenge that received a monumental solution. Examining the extraordinary remains of aqueducts, bridges, and cisterns reveals the ingenuity – and expense – committed to sating a thirsty ancient metropolis, as James Crow explains.

Aerial view of Istanbul with the Aqueduct running across the road in the foreground.
An aerial view of the Aqueduct of Valens or Bozdoğan Kemer in Istanbul, seen from the south, looking towards the Golden Horn. The 4th-century bridge is 971m long and was used up to the early 20th century. [Image: Dreamstine/Mehmet Cetin]

Camped before the walls of Constantinople, the army of the First Crusade must have been in need of a bath after slogging across the Balkans in 1097. Within the great circuit, the most powerful fortifications in Europe, was a city replete with richly decorated churches and fine monuments serving a population of possibly around a quarter of a million people, greater than any other in Europe at the time. But what most impressed William of Malmesbury, an Anglo-Norman chronicler of the Crusade, was the city’s urban water supply. This was managed through sluices and drains that cleaned the streets before emptying into the surrounding sea. Although he was writing some 30 years after the arrival of the crusaders, his account retains the contemporary legend known from Arab and other accounts that the waters were sourced at the distant Danube, delivered through hidden channels, and then dispersed through drains into the sea. Running water and urban sewers were unknown utilities in medieval towns like Paris or London, but Byzantine Constantinople retained the legacy of its 4th-century foundation and an infrastructure established by Constantine and his successors.

A map showing the course of the aqueduct channels from the distant springs west of Constantinople.

The ‘wonderful works’

Today Istanbul, astride the Bosporus waterway in both Europe and Asia, is the largest city in Europe with a population in excess of 17 million. For 1,700 years, it was an imperial city, first for the East Romans or Byzantines and, after 1453, the Ottomans. For much of late antiquity and the Middle Ages, it was among the largest cities around the Mediterranean, requiring food and water resources from great distances. Unlike Rome, which has a river, springs, and other water sources in nearby hills, Constantinople was surrounded by sea on three sides, with only a minor perennial stream and one aqueduct constructed in the time of Hadrian (reigned 117-138) to supply its predecessor, Byzantium. The new expanding city required water for the growing population and it needed a new gravity fed system to provide the water to the higher elevation of the new urban area. Two major construction campaigns in the 4th and 5th centuries resulted in the building of the most extensive water supply system in the ancient world, reaching not quite as far as the Danube, but sinuously covering 267km through the forested hills to the west of Constantine’s new city.

Map of Byzantine Constantinople, showing the two main water channels. The low-level Hadrianic line (yellow) leads to the Basilica Cistern; the high-level aqueduct (purple) runs across the Valens bridge to the Binbirdirek Cistern. The Topkapı Palace is situated on the First Hill.
Plans and sketches of the cistern
The most detailed records of the cisterns were published in 1893: this shows the İpek or Silk Cistern, probably dating from the 9th or 10th century. It is situated in the west part of the city, close to the large open reservoir of Aetius, and when documented it was occupied by Armenian spinners. Shortly afterwards, an earthquake destroyed much of the cistern, and nothing of it can be seen today.

The main visible relic of this system in the modern city is the Bozdoğan Kemer or Aqueduct of Valens, which straddles a major city highway like a giant comb separating out the traffic lanes. The bridge is 971m long, running between the city’s third and fourth hills, and originally allowed the legendary ‘Danube’ waters to reach the ceremonial heart of the city around the Great Palace, Hippodrome, and Church of Hagia Sophia. The bridge was restored a number of times by the Ottoman Sultans, and was still functioning as a water bridge into the 20th century, but remains essentially a 4th-century structure. The Aqueduct of Valens is a visible reminder of imperial munificence, both Byzantine and Ottoman, but beneath the streets of the old city are the surviving traces of more than 200 cisterns, a hidden memory of the fabric of the Byzantine city of which little survives above pavement level. The study of the ancient water features in the city goes back to the 16th century, when the first accounts appear of those Byzantine remains surviving among the new buildings of Ottoman Istanbul. However, the first serious documentation of the cisterns was published in 1893 by an Austrian Classical archaeologist and a German civil engineer. This seminal study was supplemented by further observations throughout the 20th century. The earlier Roman aqueduct of Hadrian was sourced in the Forest of Belgrade to the north-west of the city, and this fed the restored Ottoman systems until the late 19th century. Here the great 16th-century bridges built and restored by the Ottoman architect Sinan still survive, but many retain traces in their foundations of Roman and Byzantine works.

Until the final two decades of the 20th century, much less was known of the long-distance system stretching to the region known as Eastern Thrace (Trakya). A long wall from the Black Sea to the Sea of Marmora was built in the 6th century by the emperor Anastasius, 65km west of Constantinople and 56km in length, intended to provide an outer bulwark to defend the city against barbarian threats from across the Danube and the Balkans. It is a reminder that the main military danger for Constantinople and, later, for Istanbul came from the west. In more recent times – until 1990 – the region of the Long Walls and the aqueducts was a military zone, with very limited access for archaeologists or tourists. This changed with the fall of Communism, and in 1994 I was able to gain a permit from the Turkish Ministry of Culture to begin documenting the remains of the Anastasian Wall. Once we began recording the Wall structures, we became aware of the extensive remains of the aqueducts and channels preserved within the dense Thracian woodland. At the same time, the doyen of Ottoman hydraulic engineering, Prof. Kâzım Çeçen of Istanbul Technical University, turned his attention – after a career documenting Ottoman hydraulic achievements – to the Thracian aqueduct system, and the resulting study was published in 1996, in a well-illustrated volume titled The Longest Roman Water Supply Line. With the help of helicopter reconnaissance, he was able to provide for the first time a map showing the full extent of the channels and aqueducts extending past the modern town of Vize.

A rounded, stone-built channel. A person with a torch is standing, hunched over at the far end.
Water flowed towards Constantinople through vaulted stone-built channels. This example was 1m wide, with a maximum depth of 1.6m. The covered channels were lined in waterproof mortar to limit evaporation.

Very few inscriptions survive on the aqueduct bridges. One, now lost, was recorded from close to the bridge at Ballıgerme, a high single-span bridge set over a rocky gorge. The inscription dates from the early 11th century and records reconstruction of ‘the wonderful works’ after damage by nature and the enemy. Although the structure is unspecified, none other survives in the neighbourhood, and masonry from that period can be recognised in the bridge structure. Investigating the lines of the channels and bridges where they are best preserved in the forests, often with the help of local villagers, is typically slow but rewarding. During our fieldwork, conducted less than 70km from the largest city in Europe, we often felt a thrill comparable to that experienced by the discoverers of Mesoamerican monuments, as great stone bridges emerged from the Thracian forest.

Our project evolved over time. First, we were concerned to map in more detail the outline defined by Prof. Çeçen, and then to describe and document the structures and channels within a historical context, resulting in a monograph published in 2008. Another project followed, in which we worked with Istanbul Technical University to investigate the application of satellite imagery and remote-sensing. As the GPS technology improved and became more accessible, we were able to carry out higher-resolution GPS recording, which proved an important resource for our next stage. Between 2014 and 2017, we began a new project with civil engineering colleagues at the University of Edinburgh – ‘Engineering the Water Supply of Byzantine Constantinople’ – with funding for two PhD engineering students to study the channels and topography outside the city, and the distribution and storage of water within it. This was a truly interdisciplinary study that presents a rigorous basis to inform both the historical and archaeological accounts of the city.

A large aqueduct bridge surrounded by hills and overgrown with greenery.
View of the aqueduct at Kumarlidere. This is the last surviving of the 5th-century large bridges on the line towards Constantinople. To cross what is a wide valley, there were long earth embankments on either side of the bridge.

This is an extract of an article that appeared in CWA 117. Read on in the magazine (Click here to subscribe) or on our new website, The Past, which offers all of the magazine’s content digitally. At The Past you will be able to read each article in full as well as the content of our other magazines, Current ArchaeologyMinerva, and Military History Matters.

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