Based partly on the Latin ducere, meaning "lead" or "conduct," the word aqueduct named an ancient civil-engineering marvel. Ancient Rome's aqueduct system, an extraordinary feat of engineering, brought water to the city from as far as 57 miles (92 kilometers) away. Only a portion of the Roman aqueducts utilized the familiar stone arch; most were underground conduits made of stone or terra-cotta pipe. Modern aqueduct systems now often use reinforced concrete for large water mains, and ductile iron, a stronger and more elastic type of cast iron, for smaller underground pipes.