This study looks at the concepts of society, space, urbanism, expansion and organisation in the transition from Late Antiquity to the medieval period in Castile, Spain. Escalona reviews the evidence for the Iron Age and Roman antecedents in this area and details the history of fragmentation of the different territories within it, especially under the Visigoths and prior to the medieval period. Escalona discusses the development of a series of territories including Juarros, Carazo, Barbadillo and Salas, and focuses in particular on Lara which, by the middle of the 11th century, had become the main administrative center in the area, unifying many of the surrounding minor areas. Spanish text.