Behind Plaza Pilar the River Ebro, formerly known as the Iber, flows. It gives shape and personality to the city although Zaragoza has ignored its presence for quite a long time. The Ebro is the largest and longest river in Spain (though the Tagus is the largest in the Iberian Peninsula, as it flows into Portugal). It starts in the Cantabrian Mountains and flows into the Mediterranean Sea near Tortosa 900km later. It was navigable until the construction of reservoirs and had a harbour in the Roman city. Even the Normans went up it from Tortosa as far as Navarra. Five bridges cross this river in the city.