The Valens aqueduct, created to serve Byzantium (present day Istanbul), originally received a bulk of its water from the hills between Kağıthane and the Sea of Marmara (the inland sea that connects the Black Sea to the Aegean Sea). The aqueduct was a hub of of this new wide system of aqueducts and canals, built to increase the size of the eastern half of the empire. The new system eventually reached over 250 km in length, the longest such system in Antiquity. Water received from the aqueduct was stored in the city in over 100 underground cisterns. These cisterns had a total capacity of over 1 million cubic meters.[5]

While the precise start date date for construction is unknown, it is clear that it was completed in 368 AD by Roman Emperor Valens. According to local lore and tradition, the aqueduct was built using the stones of the walls of the city of Chalcedon. The stones were torn from Chalcedon's walls after the city revolted from Roman rule.

The aqueduct was again expanded after a drought in 382 AD. This “expansion line” is called the Aquaeductus Theodosiacus, after the Emperor who built it. This expansion takes water from the northeastern region known today as the Belgrade Forest

As of 1403, the aqueduct was noted by a foreign to diplomat to still be functioning in its original form. At the time, the aqueduct was well over one thousand years old. Various restoration efforts have been undertaken since 1403 and parts of the aqueduct are still in use today.