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 Ferradj eastern side. Erg Ferradj has a hot desert climate, with extremely hot summers and cool winters, and very little precipitation throughout the year. Agriculture is the main industry in Erg Ferradj. The commune has a total of of arable land found mainly to the east of the town, of which is irrigated. There are a total of 116,040 date palms planted in the commune. As of 2009 there were 9,575 sheep, 6,050 goats, 714 camels, and 23 cattle. There were also 6,400 chickens in 6 buildings. There is no significant tourist industry in Erg Ferradj. Basic services in the town