It was the first major engineering project commissioned by the Canal de Isabel II to solve Madrid's chronic water supply issues.
The dam's primary failure was due to the high permeability of the limestone substrate, which allowed water to bypass the structure entirely.
Construction involved the labor of hundreds of convicts from the local prison system.
The site was abandoned for its intended purpose only a few years after completion due to the leakage issues.
It remains one of the few examples of 19th-century hydraulic engineering in Spain that has been preserved in its original, unfinished state.
The canyon carved by the Lozoya river at this point creates a unique microclimate supporting specific plant life compared to the surrounding plateau.
El Pontón de la Oliva is a derelict mid-19th-century dam located at the confluence of the Lozoya and Jarama rivers. Constructed between 1851 and 1856, it was the first dam built to supply water to Madrid via the Canal de Isabel II. The structure stands 27 meters high and was built using large blocks of limestone. It failed as a reservoir due to significant water filtration through the surrounding karst limestone bedrock. Today, the dam serves as a popular destination for rock climbing and hiking along the canyon walls. The surrounding terrain is characterized by dramatic vertical limestone cliffs. It remains a notable industrial heritage site accessible via the GR-10 trail network. The site is currently open to the public for outdoor recreational activities.
From the trail looking up from the base of the dam to capture the scale against the river gorge.
Wear high-traction hiking boots as the limestone slopes are slippery and uneven.
Carry sufficient water, as there are no potable water sources on-site and the area can be very exposed to sun.
If visiting for climbing, check local climbing community forums for current anchor status and nesting closures.
Do not attempt to climb or traverse the top of the dam wall, as it is unstable and dangerous; avoid mid-day summer hikes due to high temperatures.
Practice Leave No Trace principles; adhere to climber-specific seasonal closures designed to protect nesting birds of prey.
