predominate, as well as intramontane valleys (located within the mountains). The plains They form extensive sedimentary basins, with a predominantly flat relief, except the eastern Llanos, which show plateaus, and the Unare depression, formed by the erosion of the mesa. Guiana Shield It exhibits a varied relief, shaped by different rocks, orogenic events and erosion over millions of years. That is why here there are peneplains, mountain ranges, foothills and the characteristic tepuis. Orinoco Delta With few contrasts, it builds a complex system of lands and waters, with varied sedimentary contributions and innumerable channels and islands. Valleys The valleys are undoubtedly the most important type of landscape in the Venezuelan territory, not because of their spatial extension, but because they are the environment where most of the country's population and economic activities are concentrated. On the other hand, there are valleys throughout almost all the national space, except in the great sedimentary basins of the Llanos and the depression of the Maracaibo Lake, except also in the Amazonian peneplains. By their modeling, the valleys of the Venezuelan territory belong mainly to two types: valleys of fluvial type and valleys of glacial type. Much more frequent, the former largely dominate the latter, which are restricted to the highest parts of the Andes. Moreover, most glacial valleys are relics of a past geologic epoch, which culminated some 10,000 to 12,000 years ago. They are frequently retouched today by fluvial events. Consequently, any attempt to categorize the Venezuelan valleys, based exclusively on the characteristics of their modeling, would be quite elementary. The deep and narrow Andean valleys are very different from the wide depressions of Aragua and Carabobo, in the Cordillera de la Costa, or from the valleys nestled in the Mesas de Monagas. These examples indicate that the configuration of the local relief is decisive in identifying regional types of valleys. Likewise, due to their warm climate, the Guayana valleys are distinguished from the temperate or cold Andean valleys by their humid environment. Both are, in turn, different from the semi-arid depressions of the states of Lara and Falcón. The Andean valleys, essentially agricultural, precociously populated but nowadays in loss of speed, do not confront the same problems of space occupation as the strongly urbanized and industrialized valleys of the central section of the Cordillera de la Costa. On the other hand, the unpopulated and practically untouched Guiana valleys are another category