Lake Chad. In the north, the Ténéré is a vast sand sheet - the true, featureless 'Ténéré' of legend reaching up to the low hills of the Tassili du Hoggar along the Algerian border. In the centre, the Bilma Erg forms rows of easily navigable low dunes whose corridors make regular byways for the azalai or salt caravans. To the west, the Aïr Mountains rise up. To the southeast, the Ténéré is bordered by the Kaouar cliffs running 100 km north to south. At the base, lies a string of oases including the famous Bilma. Periodic outcrops, such as the unusual marble Blue Mountains in the northwest near Adrar Chiriet, or the Agram hills near the oasis of Fachi and Adrar Madet to the north, are rare but notable landmarks. History During the Carboniferous period, the region was beneath the sea; later it was a tropical forest. A major dinosaur cemetery lies southeast of Agadez at Gadoufaoua; many fossils have been found there, having eroded out from the ground. An almost complete specimen of the crocodile-like reptile Sarcosuchus imperator, nicknamed the SuperCroc, was discovered there by paleontologists. During early human history, this was a fertile land much more congenial to human life than it is now. The region was inhabited by modern humans as long ago as the Paleolithic period some 60,000 years ago. They hunted wild animals and left evidence of their presence in the form of stone tools including tiny, finely carved arrow heads. During the Neolithic period about 10,000 years ago, ancient hunters, the early Holocene Kiffian people, created rock engravings and cave paintings that can still be found across the region. The Neolithic Subpluvial was an extended meteorological period, from about 7,500-7,000 BC to about 3,500-3,000 BC, of relatively wet and rainy conditions in the climate history of northern Africa. It was both preceded and followed by much drier periods. Several archaeological sites that date from this time, often identified as part of the Tenerian culture, are dotted across the deserts along the borders of Niger, Algeria and Libya. The human population dwindled as the Sahara dried out, and by 2500 BC, it had largely become as dry as it is today. In recent times, Ténéré has been a crossing route for African migrants looking to immigrate to Europe. Population The Ténéré is very sparsely populated. Fachi and Bilma are the only settlements that are not