The Águas Livres Aqueduct is a historic aqueduct, which covers 18 km and was constructed in the 18th century. King John V made the decision to build the aqueduct, to provide much needed water to Lisbon. Construction started in 1731 and in 1748 the aqueduct started to supply water to the city. The centerpiece of the aqueduct are the 35 gothic arches over the Alcantara valley. An impressive feat of Portuguese engineering and certainly worth a visit!