the romans built arenas,theaters,bridges,aqueducts,and roads more than two thousand years ago some of these constructions are still in use today why did they last so long what was the secret of roman architecture here is the answer:one of the romans' greatest inventions was the rounded arch,called the roman arch,and another was cement,a mixture of lime,clay, and water one of the early uses of the roman arch was for the construction of aqueducts,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