Aqueduct of Aguas-Libris (literally – "aqueduct of the free waters") is one of the most interesting buildings of Lisbon. This impressive engineering structure is part of the water supply system of Lisbon and across the alcântara valley in the North-Western part of Lisbon.

The aqueduct consists of 35 arches, of which 21 arch has a semicircular shape, a 14 – Lancet, the highest of which is 62 metres and 33, 7 meters in length. The aqueduct was not injured during the Lisbon earthquake in 1755 thanks to its design. The length of the aqueduct is 941 meters. He mainly runs underground and occasionally comes to the surface in the form of Grand arcades.

The aqueduct was built during the reign of Juan V who was famous for his love of all that is Grand and majestic. The appearance of the aqueduct solved the problem of water shortage in the city, which is especially sharply felt in the summer. The construction was started in 1731 and the work lasted for decades. Supervised the construction of the Portuguese engineer Manuel de Maia, who later took an active part in the reconstruction of Lisbon after the earthquake in 1755. Water through the aqueduct fell into the reservoir of Mae Aguas, and from there was distributed throughout the city.

Until the mid-nineteenth century, the aqueduct was opened the pedestrian right of way. But after it roamed a known murderer Diogo Alves (robbed the victims and threw them down), as well as cases of suicide, pedestrian walkway was closed. Today the aqueduct is open only to organized groups who agree about the tours in advance.