Travel was perilous during the Middle Ages and most of the trade and pilgrimage routes between the Mediterranean, Central Asia and Arabia were extremely dangerous. As the Frankish Crusaders attacked, these routes became even more unstable. Castles and citadels were built at strategic points, such as those at Karak and Shawbak in Jordan. Despite the political antagonism, Muslims and Franks traded with each other, crossing each others’ territories and imposing taxes on each other.