The medieval Arabic cartography of Africa outlined a paradoxical continent of facts, myth, and mystery. Ever since the great geographers such as al-Idrisi, al-ʿUmari, al-Masʿudi, and Ibn Battuta traveled to and wrote about Africa, the map of Black Africa became a combination of mystical and empirical knowledge, the result of, in the words of Paulo Fernando de Moraes Farias, “the interplay of the ideological and the cognitive.” These kinds of maps were very illustrative of certain classificatory categories in which Africans in general were known, and where cultural boundaries were drawn between more specific areas, such as Egypt and neighboring African kingdoms. Merchants and traders also contributed to the mapping of the frontier to Egypt's uppermost south, the vast territory known as bilāad al-sūdān.