Madagascar is the world's fourth-largest island, located in the Indian Ocean off the coast of East Africa. Its capital is Antananarivo. Because it has been isolated from other landmasses for over 80 million years, it has developed an incredibly unique ecosystem; more than 90% of its wildlife is found nowhere else on Earth. This includes over 100 species of lemurs and several species of baobab trees. The geography is varied, with a high central plateau, rainforests in the east, and dry deciduous forests and deserts in the west and south. One of its most famous geological features is the Tsingy de Bemaraha, a 'forest' of sharp limestone needles formed by erosion.