It is the most extensive autonomy, with 94.224 km2, which supposes 18,6 % of the national territory and more of the fourth part of the existing municipalities in Spain, since the average size of the same is the lowest than that of other communities. It is a slightly populated region, where it resides only 6,5 % of the total population of Spain.

Initially León's kingdom ensued from the Reconquest, included the lands of Galicia, Asturias, León and Castile and it had the name of Oviedo and Asturias until the year 915.

There appear landscapes of calcareous high plateau, of field and of plains with slopes and witnesses hills. All of them proved from the erosion produced by the fluvial net that has acted on soft materials and has respected the high plateaus due to the hardness of the rocks that they are formed.

The principal relief units are:

- Plains of the sedimentary basin in the center, with limy and high plateaus, and in the East, with clays, conglomerates and limy and a landscape rougher than previous forming clayey fields.

- Plains of the paleozoic socle, since, the sedimentary great basin of the river Douro is in a sunked sector of the paleozoic socle of the plateau.

The climate is continental Mediterranean, the rainfalls diminish as the altitude increases. For the latitude of the region, the Anticyclone of the Azores produces the summer drought, the Siberian anticyclon provokes a anticyclonic situation in winter with very cold masses of air.

The vegetation climax that prevails in the region is the Mediterranean forest, with oaks in hollow mount and, the gall oak on calcareous high plateaus of fresh soils. The latter coexists with the oak. The oak has moved back very much depending on species that look for bigger profitability, for the increase of culture lands and its use for fuels. Where better the oak remains is in the pastures of Salamanca.

Among the rivers of the region the most important is the Douro with the major fluvial net of Spain, with a basin of 97.290 Km2 delimited by the Cantabrian Mountain chain, the Iberian one and the Central System. The Douro is born in Urbión's peaks more than 2.000 m. high, in an area of frequent snowfalls