Park National de Isalo was established in 1962 and covers 81,540 hectares of wildly eroded sandstone massif. The grassy plains are surrounded by sandstone ridges sculpted into various wild forms, and secluded in the rocks are many Sakalava Tombs. The Canyon des Singes ('Canyon of Monkeys') makes for an interesting day walk, and you will have a good chance of seeing sifakas (a common lemur) leaping through the trees.

You can also walk along the canyon to the Piscine Naturelle - a hot and thirsty walk but worth it for the breathtaking landscape along the way. The Grotte des Portugais is at the northern end of the park. The cave isn't worth seeing, but the surrounding Forêt de Sahanafa is beautiful, with natural springs and a lot of lemurs to enjoy.

The Isalo is about 400km south-west of Tana, and the nearest town is Ranohira.