Soils and sediments are the backbone of the archaeological record and provide information about the changing form and function of spaces within castles and concerning the links between these spaces and activities in their hinterlands. In this paper, by applying a range of geoarchaeological techniques, the activities within the castle are revealed in the buried archaeological soils and sediments, and other related sites and features in the landscape, such as associated agricultural terraces and irrigation systems, from a range of frontier medieval castle sites in Spain in connection with the research project "Landscapes of (Re)Conquest: Dynamics of Multicultural Frontiers in Medieval South Western Europe", funded by AHRC.The occupation of a castle site can be dynamic. At Molina de Aragón, Guadalajara, soil micromorphological data from profiles within the citadel and the church of Santa Catalina, or Cristo de las Murallas show alternating periods of habitation occupation, abandonment and post-abandonment occupation. These microstratigraphic data show the changing nature of the occupation from Islamic to Christian, and how the occupation within the castle is reflected in the use of terraces and irrigation systems around the castle.Comparative geoarchaeological case studies show how the “Land of Aynadamar" in Nasrid Granada, was transformed following the Castilian conquest and the Christian colonization in the last peri-urban place of al-Andalus. At Cártama, Malaga, soil micromorphological analysis identified in situ corralling deposits with well-preserved dung of both larger herbivores (cattle or horses) and caprines, in an urban area during the Almohad period, which developed just below the hill where the castle is located. Remains of fodder are identifiable within the dung remains, which provides information concerning their alimentation and animal husbandry practices during the Almohad period. These strata are truncated by a pit, following the end of use of the area as a corral.