The Valens aqueduct has its origins in the Hadrianic period. Its entire length eventually extended from springs in the Thracian countryside to Constantinople, with the channel reaching 250 km long. It is the single largest aqueduct system in the Roman Empire. The impressive stretch that survives today and is visible in Istanbul is largely attributed to the emperor who completed it, Valens, in AD 368. The aqueduct bridge spans the third and fourth hills of Constantinople for almost 1000 meters, with a maximum height of 30 meters, which cars still pass through today. The structure was repaired several times in the Byzantine periods. It remained in use during the Ottoman periods (e.g., Mehmet II). The earthquake of 1509 was followed by more repairs, which continued until the 17C. Finally, the circuit was bypassed with a new distribution system in the early 20C. The aqueduct bridge stands today as a impressive monument, part of a huge circuit that once brought water from afar to the capital city was notoriously characterized by a lack of adequate natural, local water supplies.
Darius Arya streams from Istanbul detailing the impressive Valens Aqueduct