Medieval castles were, alongside the great cathedrals, the most recognisable buildings of the medieval world. Closely associated with concepts of justice, lordship and authority as well as military might, castles came to encapsulate the period's very essence. Looking at above and below-ground evidence and examining a wide variety of sites - from towering donjons to earth and timber castles - in different parts of western Europe, this book explores the relationship between early castle building and the emergence of a new aristocracy and investigates the impact of authority on the organisation of the landscape.