Situated to 700 km of Antananarivo, 243 km to Tuléar, on the RN7 in the province of Fianarantsoa and in the Fivondronana of Ranohira and Berenty Betsileo , the Park of the Isalo , the most visited park , spreads over more of 80 000km2 in the South of Madagascar. Immense eroded sandstone mountain, the Isalo comprises many deep canyons and present cavern sheltering bara tombs having formerly served as refuges to Portuguese explorers and to the Arabs traders . The South and the East of the mountain comprise deep canyons spreading on several kilometers long , and ten meters wide , with cliff that can reach near 200 m (Canyon of monkeys or Canyon of Rats). At the bottom of these gorges flow often permanent rivers. The North and the West of the mountain do not present a ruin shaped relief , but rather appear under the form of great high rocky barriers of 200 to 300 m cut of narrow and deep gorge . The important hydrographical system is constituted of clear and rapid waterways, that throw westward in the Malio, to the east in the Menamaty, both of them tributaries of the Mangoky.

The repeated action of the bush fires caused intense degradation to the mountain vegetation since many years . Fires particularly affect the slopes of the ruin shaped part of the mountain and the not - enclosed plateau where only subsist pyrophilles species, such Uapaca bojeri - Euphorbiacées, Asteropeia rhopaloides - Asteropeiacées, that reach 9 m height on the average. The grassy areas represent at least 40% of the National Park surface . The forest covers approximately 10% of the surface of the Park, localized to some slopes and to some large valley. The most current species are Uapaca bojeri - Euphorbiaceas, Asteropeia rhopaloides -Asteropeiaceas, Alberta orientalis - Rubiacées, Leptolaena multiflora - Sarcolanacées, Stereospermum euphorioides - Bignoniaceas, Acridocarpus exclens - Malpighiaceas, Dicoma incana - Astéraceas. Sticherus sp. - Gleicheniaceas grow on the gorges walls on which water streams permanently. The rupicole vegetation is abundant , distributed on the totality of the National Park and mainly marked by a kind of Pachypode (Pachypodium rosulatum - Apocynacées), a kind of Aloé (Alœ isalœnsis - Liliacées) and a kind of Euphorbe (Euphorbia duvani - Euphorbiaceas).

Prospectings in Isalo National Park have permitted to count a ten of mammals among which the Propithèque of Verreaux , Propithecus v. verreauxi, the brown Lemur , Lemur fulvus and the Lemur catta and 55 species of birds among which the Blackbird of rock Pseudocossyphus sharpei and the coua chic , Coua cristata.