The earliest author to mention Ghana is the Persian astronomer Ibrahim al-Fazari who, writing at the end of the eighth century, refers to "the territory of Ghana, the land of gold". The Ghana Empire lay in the Sahel region to the north of the West African gold fields and was able to profit from controlling the trans-Saharan gold trade. The early history of Ghana is unknown but there is evidence that North Africa had begun importing gold from West Africa before the Arab conquest in the middle of the seventh century.