The “Aqueduto da Amoreira” develops from the main spring in underground galleries (1367 Mt) and then at the level of the terrain and in arcades for more than 5.5 km that exceed 30 Mt in height. It made possible an era of progress in the city after its construction, since it supplied a multiplicity of intra-wall sources. There were problems with the water supply, made through wells located within walls and from sources in the vicinity that, in the event of war, became inaccessible. With the population increase the situation worsened. In 1498 the Elvas prosecutors asked for the intervention of D. Manuel I. The “Real d’Água” tax was levied on the city, which fell on consumer goods, in order to build an aqueduct in the future.