Though at least a proportion of them are better described as privateers, the Barbary pirates were pirates that operated out of Tunis, Tripoli, Algiers, Sal\ufffd and ports in Morocco, preying on shipping in the western Mediterranean Sea from the time of the Crusades as well as on ships on their way to Asia around Africa until the early 19th century. Their stronghold was along the stretch of northern Africa known as the Barbary Coast (a medieval term for the Maghreb after its Berber inhabitants), although their predation was said to extend as far north as Iceland, and south along West Africa's Atlantic seaboard. As well as preying on shipping, raids were often made on European coastal towns. The pirates were responsible for capturing large numbers of Christian slaves from Western Europe, who were sold in slave markets in places such as Morocco. Sultan Mawlay Ismail had a very substantial fortified palace built almost entirely by Christian slave labour obtained through the actions of Barbary pirates.