The New Student's Reference Work/Tagus

Ta′gus, the largest river of the Spanish peninsula, rises on the frontier of New Castile and Aragon, flows through Spanish and Portuguese territory, and, after 540 miles, falls into the Atlantic by an inlet at some places five miles broad.  Near its source, and also near Toledo, the river runs between rock-walls several hundred feet high.  The navigable part of the river, 115 miles, is wholly within Portugal.  Lisbon and Toledo are on the Tagus.