This spectacular wildlife film documents a remote refuge in the far north of Madagascar: the lost world of Ankarana.

In the far north of Madagascar lies the lost world of Ankarana, where lemurs dance on razor-sharp limestone and come face-to-face with the world's only cave-dwelling crocodiles. Towering 1,000 feet above the surrounding plains are walls of solid rock enclosing forests that have evolved in isolation, cut off from the outside world. NOVA goes in search of the crocodiles to discover more about their mysterious subterranean cave-dwelling habits.