The atoll is comprised of four large coral islands which enclose a shallow lagoon; the group of islands is itself surrounded by a coral reef. Due to difficulties of access and the atoll's isolation, Aldabra has been protected from human influence and thus retains some 152,000 giant tortoises, the world's largest population of this reptile.
Vallée de Mai Nature Reserve
Praslin Island, 50km north-east of Mahé.
In the heart of the small island of Praslin, the reserve has the vestiges of a natural palm forest preserved in almost its original state. The famous coco de mer, from a palm-tree once believed to grow in the depths of the sea, is the largest seed in the plant kingdom.