Aqueducts exist to this day from when they where first made and are still used today.
Arches like in the photo to the right are man made structures which still stand in Rome today.
As you can see this is a Roman highway in pompei that is used for public high or main roads, constructed and maintained at the public expense, and with their soil vested in the state. Such roads led either to the sea, or to a town, or to a public river (one with a constant flow), or to another public road. Siculus Flaccus
This is a concrete structure that the Romans made. It is possible to stand by its self and it is made of concrete. There is also the coliseum which is also made of concrete, but over time the south side has withered away from earthquakes and stone-robbers. (Seen Below)