Imagine a miniature lost world, at the top of a limestone cliff more than 600ft (180m) high. A world of razor-sharp rock spires up to 100ft (30m) tall, where the toughest boots are torn to shreds in minutes and a single false step can skin a limb or sever an artery.
A world where crocodiles live deep in underground caves, where wide-eyed lemurs peer like shy ghosts from the trees, where tiny bees attack in a viciously stinging swarm if a single member of their hive is crushed.
This is the Ankarana Plateau at the northern tip of Madagascar, and it is perhaps the most extraordinary region of the whole extraordinary island. Madagascar itself lies 375 miles (600km) from the East African coast. Measuring 1000 miles (1600km) north to south and covering 230,000sq miles (600,000sq km), it is the world's fourth largest island after Greenland, New Guinea and Borneo. Known as the 'Great Red Island' from the colour of its soil - now washing into the sea at a terrifying rate due to man-made erosion - it has evolved its plants and animals.
Its unique ecosystem began about 120 million years ago when the continents began to split apart. The map of the original supercontinent of Gondwanaland shows Madagascar sandwiched neatly between the Southern tip of India, the east coast of Africa and the northern coast of Antarctica.
In the age of the giant reptiles, dinosaurs could still plod across from Africa on dry land, and for millions of years after the split began plants and animals could float across the gap on rafts of vegetation to colonise Madagascar. But around 40 million years ago the gap become too great, and this evolutionary traffic came to an end - until about AD 500, when the first humans came on the scene, arriving by boat from Indonesia, rather than from neighbouring East Africa.
Pinnacles, Caves and Underground Rivers
The Ankarana Plateau consists of limestone scenery of the type known as Karst. Millennia of heavy rainstorms, averaging 70in (1800mm) a year, have dissolved the rock - which is soft and chalky in its upper part and hard and crystalline at its base - into spires, pinnacles and ridges, often honed to wafer thinness. The limestone is cut by deep forested canyons, where baobabs, figs and palm trees flourish, forming a green canopy 80ft (25m) overhead. More than 450 miles (720km) to the south, this landscape is repeated in the Bemaraha National Reserve in western Madagascar.
Seeping through the Ankarana rock, the rainwater has hollowed out deep caves, where lime deposits have formed spectacular stalagmites and stalactites. Streams swallowed by fissures in the limestone reappear far underground as rivers flowing through tunnels and caverns, like the vast Grotte d'Andrafiabe, where 7 miles (11km) of passages have so far been explored. The roofs of some of the larger caves have collapsed, and their floors have been colonised by plants and animals to form isolated pockets of virgin forest.
The fearsome rocks at the centre of the plateau are known locally as Tsingy from the sound they make when they are stuck, which is like the dull clanging of a cracked bell. The Malagasy (the people of Madagascar) say there is not enough level ground in the Tsingy for a single foot to be placed flat.
Brave naturalists sometimes struggle through the outer fringes of the labyrinth of rock spikes before getting hopelessly confused and beating a retreat. The few people who have tried to penetrate it say that the Tsingy is best seen from an aircraft, at a safe distance.
Most of Madagascar's wildlife is threatened by the human population's constant need for more land, but the fortress-like character of the Ankarana Plateau and the Bemaraha Reserve has so far managed to safeguard the rare creatures that live there. Several species of lemur - Madagascar's most typical indigenous mammal - live in trees which grow in crevices and sinkholes between the knife-edged rocks.