viaduct

n. Long bridge, esp. A series of arches, carrying a road or railway across a valley or hollow. [latin via way, after *aqueduct]

n. A structure of considerable magnitude, usually with arches or supported on trestles, for carrying a road, as a railroad, high above the ground or water; a bridge; especially, one for crossing a valley or a gorge. Cf. Trestlework.