The project was designed by the French engineer Carlos Lemaur to connect the Guadarrama River to the Manzanares River.
Only about 53 meters of the dam's planned 93-meter height were completed before the project was abandoned.
The collapse in 1799 occurred during a period of heavy rainfall, revealing technical flaws in the dam's mortar and foundation.
The dam utilized a revolutionary 'gravity dam' design for its time, meant to divert water to Madrid via a series of locks.
It is considered an industrial archeology landmark in the Community of Madrid.
Presa de El Gasco is a monumental 18th-century engineering ruin located at the confluence of the Guadarrama River and the Torrelodones stream. Commissioned under King Charles III, it was intended to be the tallest dam in Europe at 93 meters high to serve the Canal del Guadarrama. Construction ceased abruptly in 1799 following a partial collapse of the masonry structure. The site remains a massive, unfinished stone wall that stands as an example of Enlightenment-era hydraulic ambition. It is situated within the protected natural environment of the Guadarrama basin. The remains are currently accessible via unpaved hiking trails through scrubland and forest.
The elevated ridge trail providing a side-profile view of the massive stone wall against the river valley background.
Wear sturdy, closed-toe hiking boots, as the surrounding terrain is rocky and uneven.
Carry sufficient water, as there are no services or potable water sources in the immediate vicinity.
Visit during the spring or autumn to avoid the intense heat of the Madrid summer.
Attempting to visit during the hottest hours of the day in summer or immediately after heavy rain when trails become muddy and slippery.
Practice 'Leave No Trace' principles; do not climb on the unstable historical masonry ruins.
