Portugal, Alentejo, Elvas. A 6 km long aqueduct supplies the city of Elvas with pure water; it was begun early in the 15th century and completed in 1622. For some distance it includes four tiers of superimposed arches, with a total height of 40 m. Elvas lies on a hill 8 km northwest of the river Guadiana. It is defended by seven bastions and the two forts of Santa Luzia and Nossa Senhora da Gra_a.