The "Free Water" aqueduct, built between 1732 and 1748, still supplies Lisbon's water today. It measures a total of 58km with 35 of its arches spanning the Alcântara Valley. The tallest of these is 65m high, with a span of 29m. The best view of this masterpiece by architect, Manuel de Maiais, is from Avenida de Ceuta, north of the N7 motorway bridge.