On May 12 1731, D. Joao V authorised the construction of the Aguas Livres Aqueduct by royal decree. Construction began in August 1732 and in 1748 the Aqueduct was operational. The length of the Aqueduct, including all its branches, is 58,135 metres. Besides being used to supply water to Lisbon, the Aguas Livres Aqueduct, also provides an access point to the city. The two sidewalks on the top of the Alcantara Valley arches are still used. This is a series of 35 arches – 14 ogival and the remaining ones in perfect turn – it is 941 metres in length. The largest arch is 65 metres high and 32 metres wide. Withdrawn from the supply system in 1967, the Aqueduct is one of the most remarkable works of the hydraulic engineering ever.