The emblematic Águas Livres Aqueduct, a complex system for collecting, supplying and distributing water to the city of Lisbon, was built by order of King João V in the 17th century. Originating at the Águas Livres spring, in Belas, in the municipality of Sintra, it was reinforced and extended throughout the 19th century. Despite the earthquake of 1755 having shaken the city of Lisbon, the Águas Livres Aqueduct resisted unscathed. Classified as a National Monument since 1910, it is considered a remarkable work of hydraulic engineering.