Built in 1746, Lisbon’s remarkable aqueduct delivered the first clean drinking water to the city. The full pipeline is some 18.6 km long, although the aqueduct and its tributaries total 58km. The most visible section is that crossing the Alcantara Valley with 14 massive arches, the tallest of which is over 60 m from the ground. The best viewing point is the Campolide Station. Declared a National Monument in 2002, the fact that it survived the great earthquake of 1755 is testimony to its solid construction.