Grand Erg Oriental follow the wind's direction. There are other types of dunes, as well as "complex" dunes. Saharan winds are also known to clear an area of sand altogether, leaving bare rock (hamada) or gravel (reg). The "Grand Erg Oriental" is accessible overland by an Algerian road, which goes south from Constantine. It passes through the Aurès mountains, then salt lakes by the city of Biskra. Next the road skirts the western edge of the erg. After about 500 km. in all, it reaches the ancient oasis of Ourgla [Wargla]. Since late antiquity Wargla was a stop for the Saharan trade, being
International Association of Arabic Dialectology International Association of Arabic Dialectology The International Association of Arabic Dialectology (, AIDA) is an association of researchers in Arabic dialects, from all over the world. AIDA was founded in 1992, in Paris, at the initiative of a group of prestigious Arabists, with the aim to encourage and promote the study of Arabic dialects. AIDA is nowadays the leading international association in this field of research and it has become a center that joins scholars from all over the world who are interested in any aspect of Arabic dialectology, including dialects which have not been described yet, dialectal geography, specific