Let me put it this way, Lisbon’s medieval city was mostly destroyed by the 1755 earthquake. And the Aguas Livres Aqueduct, built to bring water from nearby Sintra, 14 km away, survived the cataclysm, just after being finished, in 1748. Miraculously it was one of the few great buildings that didn’t collapse.
It is the biggest, if not the widest Lisbon monument in sight. And probably, the oldest. And having the privilege to walk on this historical site is an amazing experience. It’s a huge architectural piece of history, which is the exact same way it was almost 300 years before.
We get to see the views from both sides, since it has two paths that connect in the middle. And down bellow we get to see these very picturesque small neighborhoods, really very different from the rest of the city. You get a great view over the Alcantara valley, with Lisbon on one side and Monsanto forest and the “25 de Abril” bridge on the other. The walkable part of the aqueduct connects Amoreiras to Monsanto forest. Unfortunately the Monsanto exit is normally closed. Otherwise, it would be another great shortcut, as is the Green Corridor.
Save this spot for the sunny or dry days. And try to save enough time for a long walk. You will do a lot of contemplating!