Aqueduto das Aguas Livres (Free Waters Aqueduct), Lisbon

Considered the most breathtaking sight in Lisbon during the early 20th century, the majestic Free Waters Aqueduct stands prominently over the Alcântara valley in the northwest of the city. Its construction allowed the Portuguese Sun King, João V, to indulge in his passion for grandiose building projects, as the only area in Lisbon with access to fresh drinking water was the Alfama district.

The project was financed through a tax on various food items such as meat, wine, and olive oil. Although it was not fully completed until the 19th century, the aqueduct began supplying water to the city as early as 1748. Spanning a distance of 60km, with the majority of it underground, it successfully withstood the devastating 1755 earthquake. However, it later gained notoriety due to the actions of Diogo Alves, a 19th-century serial killer who would throw his victims off the top of the aqueduct, resulting in a fatal 70-meter drop.

The most prominent feature of this impressive structure is its 35 arches that span the Alcântara valley. Guided tours are available to explore them, although they require a head for heights. Visitors can also take tours of the Mãe d'Água reservoir and visit the Mãe d'Água springs (for more information about these tours, contact the Museu da Água).

At the end of the aqueduct, you'll find the Mãe d'Água das Amoreiras, a castle-like building that once served as a reservoir for the water supplied by the aqueduct. Today, the space is used for art exhibitions, fashion shows, and other events.