The Rif mountains stretch over the region bordering the Mediterranean from the north-west to the north-east. The Atlas Mountains run down the backbone of the country, from the northeast to the south west. Most of the southeast portion of the country is in the Sahara Desert and as such is generally sparsely populated and unproductive economically. Most of the population lives to the north of these mountains, while to the south lies the Moroccan Sahara, a former Spanish colony that was liberated by Morocco in 1975 (see Green March). Morocco claims that the Moroccan Sahara is part of its territory and refers to that as its Southern Provinces.