The low Valley of the Lozoya represents one of the most peculiar sub-county of the Sierra Norte de Madrid, where the Lozoya River and its waters becomes a resource of great importance. Precisely, the course of the Lozoya has been affected in the second half of this century by the different reservoirs that the Canal de Isabel II has built in it to cater to the supply of water of Madrid.

Specifically, Puentes Viejas reservoirs are in the low Valley of the Lozoya, The darker, Del Villar and the Atazar. The rest of the hydraulic infrastructures, dams, channels, etc., in the area are a true reflection of the importance of water as a natural and economic resource.

The terrain is generally hilly, Although the heights are moderate and some steep areas. They dominate the boards, and the floors are in general poor. The vegetation is dominated by the jaral, Although in some areas you can find splendid oak and pine forests like for example those in the municipal district of old bridges. As unique formations we can find typical vegetation of ribera as the Aliseda de Mirabel or the Aliseda of Riata, as well as poplars, Ash, etc., around the cross Canal de Lozoya.

The nuclei of population belonging to this subregion is characterized by important livestock vocation, today in recession, and that you have configured a characteristic architectural typology that dominate the traditional elements and agricultural constructions. Depopulation has affected all the nuclei with the consequent abandonment of the traditional activities. In recent years have promoted an important alternative activities such as the development of the "Rural tourism".

The entire region has natural and environmental resources of great value, as evidenced by the fact that part of it is within the national reserve of Sonsaz hunting, where can we find a variety of faunal resources.

The recommended access to the low Valley of the Lozoya, It may be done through the NI de Burgos, Turning off well in La Cabrera, taking the M-127 road to the town of El Berrueco, from where we can access the rest of the municipalities of the region. The deviation in the Burgos NI can be done also in Lozoyuela, taking the M-135 that goes to Mangiron, either the M-131 you arrive to El Berrueco. Since both cores, we can access the rest of the sub-region.