Glimpsed through the haze of the imagination, hidden behind vast expanses of jungle, desert, and grassland, the mountains of Africa crystallize in rock – and traces of equatorial snow – the aura of mystery that imbues the continent with its special mystique. Just south of the Mediterranean, the Atlas Mountains rise in a great wall of folded ranges, barring the way to the empty wastes of the Sahara. Deep in the sands of the world’s largest desert, undulating in waves of heat, stand the gaunt pinnacles of the Ahaggar and Tibesti massifs. Like most of the mountains of Africa, other than the Atlas and the Ruwenzori, they were formed by volcanic activity. Remnants of ancient lava flows sprawl over other parts of the continent, capping the serrated ranges of South Africa and covering the highlands of Ethiopia.