Technology
The ancient Romans also had a complex system of aqueducts, which were used to transport water across long distances. The first Roman aqueduct was built in 312 BCE. The eleventh and final ancient Roman aqueduct was built in 226 CE. Put together, the Roman aqueducts extended over 450 kilometers, but less than seventy kilometers of this was above ground and supported by arches.
Valens Aqueduct
The exact date that construction on the aqueduct began is uncertain, but it was completed in 368 AD during the reign of Roman Emperor Valens, whose name it bears. The spectacular bridge section lay along the valley between the third and fourth hills of Constantinople, occupied respectively at that time by the Capitolium and the Church of the Holy Apostles. According to tradition, the aqueduct bridge was built using the stones of the walls of Chalcedon, pulled down as punishment in 366 after the revolt of Procopius. The structure was inaugurated in 373 by the urban prefect Clearchus, who commissioned a "Nymphaeum Maius" in the Forum of Theodosius, that was supplied with water from the aqueduct.