Bozdoğan Arch
Information about the first construction of the Bozdoğan Aqueduct is not certain. It is known that some water facilities were built in Istanbul around 123 during the reign of Roman Emperor Hadrian, but it is not clearly understood to what extent the Bozdoğan Aqueduct is related to these. After the city was re-established by Constantine I in 300, the facilities were also renewed. It is generally accepted that the arch was built by the Roman Emperor Valens (364-378) and for this reason it is also known as the "Valens Aqueduct".It has not yet been clarified when and on what occasion the work, which is mentioned only as Kemer in the Fatih foundation deeds, got its current name.
The original technical features of the Bozdoğan Aqueduct, built with regular cut stones, can be seen in the 25th chamber, which has remained in the best condition.
Bozdoğan Aqueduct, one of the oldest works of Istanbul, helped meet the city's water needs during the Late Roman and Byzantine periods and continued this service as a part of the city's water network throughout the Ottoman period.
Source Türkiye Culture Portal History of Istanbul