Built in 1778 to carry water from the park’s lake to irrigate the Huerta de la Partida, this brick-arched aqueduct in Madrid’s Casa de Campo was designed by Francisco Sabatini — the same royal architect behind the Puerta de Alcalá and the Palacio Real. It’s the oldest of several aqueduct remnants scattered through the park, restored in 2016 and now standing beside a public path near the lake, walkable and almost entirely unknown even to locals.