A viaduct's a bridge composed of several small spans. The term viaduct's derived from the Latin via for road and ducere to lead something. However, the Ancient Romans didn't use that term per se; it's a modern derivation from an analogy with aqueduct. Like the Roman aqueducts, many early viaducts comprised a series of arches of roughly equal length. Viaducts may span land or water or both. The longest viaduct in antiquity may have been the Pont Serme which crossed wide marshes in southern Fran… (More on Viaduct)