The Aqueduct of Valens, also known as the Bozdoğan Kemeri, is a Roman aqueduct built in Istanbul to supply the capital of the Eastern Roman Empire. It stands as one of the most important historical monuments of the city, stretching across the valley between the hill currently occupied by Istanbul University and the hill of the Fatih Mosque.
The construction of Istanbul's water supply system began under Emperor Hadrian, but the rapid growth under Constantine the Great necessitated a much larger network. The aqueduct's construction started during the reign of Constantius II and was completed in 378 under Emperor Valens. According to tradition, the stones of the pulled-down walls of Chalcedon were used to build the structure, which was inaugurated in 373 by urban prefect Clearchus.
This monument formed the terminal point of an extensive water supply network stretching hundreds of kilometers from Thrace. Once water reached the capital, it was stored in numerous underground cisterns, such as the Basilica Cistern, and open reservoirs. Over the centuries, rulers including Theodosius I, Justinian the Great, and Justin II undertook various restorations and expansions.
During the Byzantine period, the aqueduct suffered damage from the Avar siege and earthquakes, leading to major repairs by emperors such as Constantine V and Basil II. Although it fell out of administrative focus during the Latin Empire and Palaiologan period due to a declining population, records from travelers like Ruy Gonzáles de Clavijo confirm it was still functioning in 1403.
Following the conquest of Istanbul, Ottoman Sultan Mehmed the Conqueror repaired the system to supply the Old Palace and Topkapı Palace. After damage from the 1509 earthquake, repairs continued, and in the 16th century, Suleiman the Magnificent commissioned Mimar Sinan to connect water from the Belgrade Forest, feeding the Kırkçeşme water distribution network.
The surviving section of the aqueduct spans 921 meters, featuring a consistent slope and an engineering design utilizing both ashlar blocks and bricks. The lower tier consists of squared stone blocks, while the upper tier utilizes stones clamped with iron. Pillars and arches cross directly over modern Atatürk Boulevard.
Today, the Aqueduct of Valens remains a prominent landmark in Istanbul. Visitors encountering the monument today observe its towering double-tiered arches bridging the urban landscape, carrying forward an unbroken legacy of ancient engineering into the modern metropolis.
Wikimedia research dossier · Last checked: 2026-09-12 17:42:49
