Guadiana, an important river of Spain, has its source in the E. of the plateau of Mancha, and for a short distance is known as the Zancara, flows in a westerly direction as far as Badajoz, where it bends to the S., then forms the border between Portugal and Spain for a short distance, bends into Alemtejo, and again, ere reaching the Gulf of Cadiz, divides the two countries; it is 510 m. long, of which only 42 are navigable.