As part of an ongoing research project into the fortifications of the Balearic Islands, it is becoming clear that castral space of medieval Mallorca was a highly dynamic space, the fabric of which was in a near constant state of flux, relative to the strength of the island's central government. The juxtaposition of a 'cosmopolitan' urban centre and an agrarian, practically mono-cultural, hinterland created a situation of constant tension in which fortifications played a central role. During the Islamic period the castles of the Balearics protected against foreign attackers as well as from central control, and it the study of is this duality of purpose which allows us to further our understanding of Andalusian society and how it was integrated into the feudal system of its Christian conquerors.