one of the early uses of the Roman arch was for the contruction of aqueduct, which carried water to cities. Usually, an aqueduct had several levels of arches. The Romans often placed the larger and wider arches in the bottom row for support, and the smaller and narrower arches were on the top level. Also, on the top, they placed a lead U-shaped pipe along which the water flowed, thanks to the pull of gravity. One of the best-preserved Roman aqueduct is at pont du Gard in France. It was built in 19 B.C.E.