Now nothing more than a scenic overpass for cars traveling down Atatürk Bulvari, the Valens Aqueduct or "Arcade of the Gray Falcon" was started by Constantine and completed in the 4th century A.D. by Valens. Justinian II had the second tier added; even Mehmet the Conqueror and Sinan had a hand in its restoration and enlargement. The aqueduct connects the third and fourth hills of Istanbul and had an original length of about .8km (1/2 mile). Water was transported under various rulers to the Byzantine palaces, city cisterns, and then to Topkapi Palace, and the aqueduct served in supplying water to the city for a total of 1,500 years.