San Buenaventura Mission Aqueduct
The San Buenaventura Mission Aqueduct was a seven-mile long, stone and mortar aqueduct built in the late 18th and/or early 19th century to transport water from the Ventura River to the Mission San Buenaventura in Ventura, California. Accounts vary greatly as to when the aqueduct was built.
Source: Wikipedia — San Buenaventura Mission Aqueduct (CC BY-SA 4.0)