Locks 17-18-19-20

Locks 17-18-19-20, built between 1759 and 1804, form a quadruple lock system that overcomes a total difference in elevation of 14.36 meters by means of oval-shaped limestone basins, with lengths between 18.30 and 18.60 meters and widths of approximately 9.50 meters. The system includes spillways, intakes, and buried conduits that regulated the flow and allowed water to be diverted to the adjacent buildings. The diversion channel, 4 meters wide and 1.70 meters deep, lined with limestone, carried water to the factories before returning it to the main canal and is still in good condition.

The complex includes several bridges: the main bridge, a semicircular arch built of limestone ashlar, partially renovated; and three bridges on the diversion, one blocked, another located 300 meters downstream, and a third aligned with the main bridge, with a central arch and two lateral culverts. All retain their original construction. Among the buildings, the warehouse (44 m long), the caretaker’s house (square floor plan), the stable, and the offices of the Hydrographic Confederation stand out, all restored and built with ashlar foundations, wooden structures, and curved tile roofs. The lock keeper’s house, made of plastered brick and rammed earth, is preserved but not in optimal condition. The mill, with its four-arched arcade, is in poor condition, while the fulling mill, rebuilt, maintains its rectangular floor plan and ashlar and rammed earth walls. The Frómista Canal intake, the hydroelectric power station, and the railway bridge complete the complex, illustrating the evolution of water use from the 18th century to industrialization.

It is a perfect place to stroll at a leisurely pace and discover how enlightened engineering transformed the territory, leaving a heritage that still converses with the serenity of the Frómista landscape.