Pinilla Reservoir, Reservoir on the Lozoya River, Iberian Peninsula

Pinilla Reservoir is a large body of water in the Community of Madrid built to store water for nearby towns and farmland irrigation. Walking paths line its edges, often shaded by trees and easy to follow, while ducks and other waterfowl float on the surface or rest along the banks.

The reservoir was opened more than fifty years ago to store water from the Lozoya River for supplying towns and irrigation needs. Its construction transformed the valley by flooding areas that previously held houses and farmland, reshaping the landscape for a new water storage system.

The reservoir takes its name from Pinilla del Valle, the village beside the dam, and its 1,090 m crest was fixed so the water would not reach the villages of Pinilla del Valle and Lozoya; 12 buildings were flooded anyway. Since 1992 a small hydro plant and a drinking-water treatment station share the intake tower at the foot of the dam.

The reservoir is accessible year-round with easy, shaded trails for walking and open views of the water and surrounding land. The best conditions for visiting are early mornings or weekdays when the area is quieter and the natural setting feels less crowded.

The dam's crest sits at 1,090 metres above sea level, a height fixed by the presence of Pinilla del Valle and Lozoya; even so, 12 buildings were flooded. The reservoir was the first Canal de Isabel II facility to use ozonation and granular activated carbon filtration, added after algae caused odour and taste problems.