Douro
one of the largest rivers of Spain and Portugal, rises in the Pico de Urbion (7,369 feet), in Old Castile, about 30 miles N. W. of Soria (3,445 feet above sea-level). From its source it flows S. E. to Soria, then winds toward the W. and pursues a general W. direction till it reaches the Portuguese border, when it flows S. W. for about 60 miles, forming the boundary beboundary be tween Spain and Portugal, and then flows W. through Portugal, entering the Atlantic below Oporto. Its Portuguese tributaries are comparatively small. The total length of the river is about 490 miles; it is navigable to Torro de Moncorvo, 90 miles.