GUADALQUIVIR (ancient Baetis, Moorish Wadi al Kebir, "the Great River"), a river of southern Spain. What is regarded as the main stream rises 4,475 ft. above sea-level between the Sierra de Cazorla and Sierra del Pozo, in the province of Jaen. It does not become a large river until it is joined by the Guadiana Menor on the left, and the Guadalimar on the right. Below Coria it traverses the series of broad fens known as Las Marismas, the greatest area of swamp in the Iberian Peninsula. Below Sanlucar the river enters the Atlantic after a total course of 36o m. It drains an area of 21,865 square miles. In the time of the Moors it was navigable up to Cordova, but owing to the accumulation of silt in its lower reaches it is now only navigable up to Seville by vessels of 1,200 to 1,50o tons. Navigation has now been facil itated by the new cut, known as the Corte de Tablada, and swing open bridge.