EBRO (anc. Iberus or Hiberus)  , the only one of the five great rivers of the Iberian Peninsula (Tagus, Douro, Ebro, Guadalquivir, Guadiana) which flows into the Mediterranean . The Ebro rises at Fuentibre, a hamlet among the Cantabrian Mountains, in the province of Santander; at Reinosa, 4 M. east, it is joined on the right by the Hijar, and thus gains considerably in volume . It flows generally east by south through a tortuous valley as far as Miranda de Ebro, passing through the celebrated Roman bridge known as La Horadada (" the perforated "), near Ofla in Burgos . From Miranda it winds south-eastward through the wide basin enclosed on the right by the highlands of Old Castile and western Aragon, and on the left by the Pyrenees . The chief cities on its banks are Logrono, Calahorra, Tudela, Saragossa and Caspe . Near Mora in Catalonia it forces a way through the coastal mountains, and, passing Tortosa, falls into the Mediterranean about 8o m. south-west of Barcelona, after forming by its delta a conspicuous projection on the otherwise regular coast line . In its length, approximately 465 m., the Ebro is inferior to the Tagus, Guadiana and Douro; it drains an area of nearly 32,000 sq. m . Its principal tributaries are—from the right haid the Jalon with its affluent the Jiloca, the Huerva, Aguas, Martin, Guadalope and Matarrana; from the left the Ega, Aragon, Arba, Gallego, and the Segre with its intricate system of confluent rivers . The Ebro and its tributaries have been utilized for irrigation since the Moorish conquest; the main stream becomes navigable by small boats about Tudela; but its value as a means of communication is almost neutralized by the obstacles in its channel, and seafaring vessels cannot proceed farther up than Tortosa . The great Imperial Canal, begun under the empercr Charles V . (r 5oo-1558), proceeds along the right bank of the river from a point about 3 M. below Tudela, to El Burgo de Ebro, 5 M. below Saragossa; the irrigation canal of Tauste skirts the opposite bank for a shorter distance; and the San Carlos or New Canal affords direct communication between Amposta at the head of the delta and the harbour of Los Alfaques . From Miranda to Mora the Bilbao-Tarragona railway follows the course of the Ebro along the right bank .