This beautiful walk runs along the banks of the Pedrezuela reservoir and is very popular with the inhabitants of Guadalix de la Sierra and the people of Guadalix de la Sierra. Its lack of gradient and the good condition of the path make it suitable for children, pushchairs and it can also be done by bicycle.

Leaving from the Tourist Office, we head towards the Town Hall Square. The façade of the Town Hall has a large balcony, plus a railing that runs along the entire front of the building. The balcony of this main façade became famous thanks to Pepe Isbert, who in the famous film "Bienvenido Mister Marshall" (1952) gave from it his well-known and remembered speech which began with the famous phrase "...As your Mayor, I owe you an explanation,...". We take Calle Egido for about 150 metres, and turn right to take the Carretera Vieja del Pantano and its extension Paseo de la Ermita.

The Paseo de la Ermita runs for the most part through the shade of ash and poplar trees and will take us towards the reservoir area, leaving the "green filter" to the left, a piece of land that was once used for the natural purification of waste water from Guadalix de la Sierra. The territory of Guadalix de la Sierra is rich in underground waters that rise to the surface forming springs and fountains. On reaching the reservoir we pass the springs of El Espinar and El Pilacón. Both springs offer very high quality water, of deep and safe origin according to the 1830 project.

The waters of El Pilancón were used to supply the town and to irrigate part of the fertile plain that was cultivated in the past. A few metres further on, on our right, we come to the hermitage of Nuestra Señora de El Espinar, built on a 400 square metre estate called Las Cabezadas, which was donated altruistically by a neighbour. The interior of the hermitage is home to the patron saint of the village, the Virgen del Espinar, who only leaves her dwelling at Easter for the procession of the Encounter and in September for the celebration of her Patron Saint's Day. The original hermitage, which has now disappeared, was in what is now the heart of the reservoir.

We continue along the path along the Pedrezuela reservoir, bordered by riverside vegetation such as alders and poplars. On its banks it is common to observe a multitude of waterfowl and waders, many of them migrating. We can also find animals such as otters, marsh harriers, red-crested pochards and marsh bunting. We can also observe birds far from the riverbank such as eagles, black vultures, white storks and peregrine falcons. The route continues along the fishing preserves. These waters are a paradise for fishing for common carp, royal carp, carpin, tench, pike, trout or perch. Approximately 1500 metres from the hermitage, the path bends to the right and we enter the area called Paso del Arroyo Saelices. Along the stream we cross a holm oak forest, and to our right at the top of the slope we discover the Abrigo de Peña Rubia where we can see the cave of the same name and the end of the walk.