Traditional hydraulic milling was the main productive activity in the Sierra de Cádiz (Andalusia, Spain), as evidenced by the existence of 85 mills spread throughout the region. Although the date of their construction is unknown, the first documentary evidence of their existence appeared in the 16th century. In the 18th century, a more comprehensive account of the set of mills in the Sierra was drawn up thanks to the Ensenada Cadastre. The majority were operational until the mid-20th century, albeit with some difficulties. The disappearance of this handmade trade has led to the obsolescence and abandonment of its architecture and infrastructure. However, the infrastructure remains there, as traces of a recent past in which it is still possible to see the Circular Water Story that made them work. This article explains the hydraulic system that was used by the mills in the Sierra de Cádiz. Located next to rivers and streams, they formed part of an open water re-circulation system, which captured the water at a specific point in the riverbed of origin, artificially diverted it to the mill and then ended up returning it to the same riverbed of origin, at a different point from the initial one. The methodology used is based on the preparation of graphic documents and photographic recognition to select the riverbanks that show the adaptations and variations of the water re-circulation system according to the hydrographic, topographic, and productive characteristics of each territory. As some of these old artificial riverbeds are still operational, today they are used as a natural resource to supply water to other productive activities, thus proving the usefulness of the system, the suitability of the construction techniques applied, and their consequent integration into the landscape. The research carried out justifies the need to protect and catalogue these architectural hydraulic systems before they disappear completely, in order to benefit from the learning that can be derived from the reading, interpretation, and transformation of the territory and its landscape
