One of the early uses of the Roman arch was for the construction of aqueducts,which carried water to cities.Usually, an aqueducts 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 flower, thanks to the pull of gravity.
One of the best-preserved Roman aqueducts is at Pont du Gard in France. It was built in 19 B.C.E.