A keep is a type of fortified tower built within castles during the Middle Ages by European nobility. Scholars have debated the scope of the word keep, but usually consider it to refer to large towers in castles that were fortified residences, used as a refuge of last resort should the rest of the castle fall to an adversary. The first keeps were made of timber and formed a key part of the motte-and-bailey castles that emerged in Normandy and Anjou during the 10th century; the design spread to England, Portugal, south Italy and Sicily. As a result of the Norman invasion of 1066, use spread into Wales during the second half of the 11th century and into Ireland in the 1170s. The Anglo-Normans and French rulers began to build stone keeps during the 10th and 11th centuries, including Norman keeps, with a square or rectangular design, and circular shell keeps. Stone keeps carried considerable political as well as military importance and could take a decade or more to build.
The Norman (c. 1126) keep of Rochester Castle, England (rear). The shorter rectangular tower attached to the keep is its forebuilding, and the curtain wall is in the foreground.
Reconstructed wooden keep at Saint-Sylvain-d'Anjou
The Norman keep at Colchester Castle in Essex, built in a Romanesque style on the foundations of a Roman temple
The Norman keep (r) and prison (l) at Goodrich Castle in Herefordshire, England, built to a square design in the early 12th century
A castle is a type of fortified structure built during the Middle Ages predominantly by the nobility or royalty and by military orders. Scholars usually consider a castle to be the private fortified residence of a lord or noble. This is distinct from a mansion, palace and villa, whose main purpose was exclusively for pleasance and are not primarily fortresses but may be fortified. Use of the term has varied over time and, sometimes, has also been applied to structures such as hill forts and 19th- and 20th-century homes built to resemble castles. Over the Middle Ages, when genuine castles were built, they took on a great many forms with many different features, although some, such as curtain walls, arrowslits, and portcullises, were commonplace.
Dating back to the early 12th century, the Alcázar of Segovia, Spain, is one of the most distinctive castles in Europe.
Built in 1385, Bodiam Castle in East Sussex, England, is surrounded by a water-filled moat
The Norman White Tower, the keep of the Tower of London, exemplifies all uses of a castle including city defence, a residence, and a place of refuge in times of crisis.
Windsor Castle in England was founded as a fortification during the Norman Conquest and was one of the principal official residences of Queen Elizabeth II during her reign.