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
Erg Chech to the Tuareg people, the elliptical strewn field stretches for more than . Erg Chech The Erg Chech (), is a large erg in southwestern Algeria and northern Mali. It is an almost uninhabited part of the greater Sahara Desert, an inhospitable desert region with long, extremely hot summers and short, very warm winters. The Erg Chech is a vast sandy expanse including compound and complex linear and star dunes. The mean elevation of the Erg Chech is just above 300 m, slightly lower than the neighboring Erg Iguidi stretching to the north. The barren plain of the Tanezrouft is