The dunes of Erg Chebbi reach a height of up to 150 meters in places and altogether spans an area of 50 kilometers from north to south and up to 5-10 kilometers from east to west lining the Algerian border.
The nearest sizable town is Erfoud, about 60 kilometers further north. One other city is Rissani, around 40 kilometers from Merzouga, and from the 8th to the 14th century there was a separate kingdom, known as Sijilmassa, which was prosperous owing to former caravan routes.