Ardèche is a part of the region Rhone - Alpes. It is bordering departments of Drôme, Vaucluse, Gard, Lozère, Haute Loire, Loire and Isère.
Grounds, climate and vegetation of Ardèche are very different between the North and the South of the department, which is so characterized by its big variety of natural circles and landscapes, whereas the department extends over a steep slope of more than 1000 metres of made uneven, separating the high plateau of the Central Massif and the valley of the Rhone near to Valence. 45 % of the territory is occupied by forests.
* The North ( Haut-Vivarais) is rather crystalline, wet and green. This country of high hills and low mountain ranges belongs to the Central Massif. The pond of Eyrieux, until the neighborhoods of juices and mountain Mézenc, forms " Boutières ". Some rare dolmens and menhirs are known in this geographic zone.
* The South ( Bas-Vivarais) is marly or calcareous, drier, with an already Mediterranean vegetation. The pond of Ardèche digs there spectacular throats. The subterranean waters are numerous, characteristics of the karstic circles: aven of Orgnac, Saint Marcel's cave, aven of Noël. Hills and plateau des Gras are connected geologically with the "Grands Causses" big Limestone plateaus ( about 50 dolmens). It is in the South of Ardèche that concentrate more than 800 dolmens and some rare menhirs (between 5 and 10), all in limestone.
Some granite menhirs ( less than 10 ) and some dolmens in schist ( less than 5 ) are known on the Cévennes part of Ardèche.
* In the centre of the department, the basalts of the plateau of Coiron and marls and limestones of Moyen-Vivarais form a sort of space of transition, geologic history of which is very complex.
No megaliths in this part of Ardèche as well as on the part " ardéchoise" of the valley of the Rhone named " le Rivage" (the Bank), a plain of alluviums of different ages, punctuated with villages and with towns, in the centre of fertile agricultural soils.