Sandstone is sedimentary rock made from small grains of minerals, quartz and feldspar. It often forms in layers which can be seen on the cliff walls.
Isalo's landscape consists of eroded sandstone formations dating to the Jurassic period, deep canyons with riparian forests, palm-lined oases, fire-resistant tapia forests, and open grasslands. The grassy plains are surrounded by sandstone ridges sculpted by wind and water into wild forms, and secluded in the rocks are many Sakalava Tombs. In places the landscape can give the sensation of being transported to the old wild west. It's one of the country's most spectacular regions, perfect for overnight hikes and rock-climbing.
Although animal life isn’t the park’s most prominent feature, there are a few species to look out for, including two species of lemur: ringtail and brown lemur, and Verreaux’s sifaka. Isalo National Park is also home to approximately 55 species of bird, including the rare Benson’s rock-thrush.
Those equipped for trekking and camping can spend several days or longer wandering around the Isalo Massif. Two popular sites are only a day’s hike from the main gate. At Canyon des Singes & Piscine Naturelle natural pools provide a perfect swimming opportunity. At Natural Window, the sandstone has formed a square hole in the rock, giving the illusion of window. Watching the sun rise or set through the window is a popular activity, so it may get busy.