San Juan Reservoir

San Juan Reservoir is a man-made lake on the Alberche River in the western part of the Community of Madrid, surrounded by pine forests and mountain ranges in the background. The shore includes quiet coves with sandy beaches, rocky sections, and several small harbors for leisure boats.

The dam was built in the mid-1950s to secure the water supply for several municipalities in the region. Shortly after completion, the area was opened for recreational use, which boosted tourism in the surrounding countryside over the following decades.

The reservoir's name comes from a small village that was submerged when the dam was built. Families now gather along the shore for picnics and day trips, while water sports enthusiasts use the open water for jet skiing and motorboating.

The main access points are on the south side near San Martín de Valdeiglesias, where paved roads lead to parking areas and public bathing spots. Weekends in summer draw many visitors, so arriving in the morning is advisable.

In the shallower areas, old tree stumps and wall remnants from the submerged village grow underwater, becoming visible when water levels drop. Divers explore these ruins and search for traces of former houses and paths.