However, it is the rock art (engravings and paintings) that have made Tassili world famous as from 1933, the date of its discovery. Criterion (iii): The rock art images cover a period of about 10,000 years. Criterion (viii): The geological conformation of Tassili n'Ajjer includes Precambrian crystalline elements and sedimentary sandstone successions of great paleo-geographical and paleo-ecological interest. The rock art of Tassili n'Ajjer, is the most eloquent expression of relationships between humans and the environment, with more than 15,000 drawings and engravings testifying to climate changes, wildlife migrations, and the evolution of humankind on the edge of the Sahara. The property management also reflects the strong regional value of Tassili n'Ajjer as one of the essential elements of an ecological belt, which includes plant and animal species typical of the Sahara, as well as tropical and Mediterranean species, adapted to the rigors of the climate.