Blonde Girl Posing In A Castle On The Table

A keep was a great tower and usually the most strongly defended point of a castle before the introduction of concentric defence. "Keep" was not a term used in the medieval period – the term was applied from the 16th century onwards – instead "donjon" was used to refer to great towers, or turris in Latin. In motte-and-bailey castles, the keep was on top of the motte. "Dungeon" is a corrupted form of "donjon" and means a dark, unwelcoming prison. Although often the strongest part of a castle and a last place of refuge if the outer defences fell, the keep was not left empty in case of attack but was used as a residence by the lord who owned the castle, or his guests or representatives. At first this was usual only in England, when after the Norman Conquest of 1066 the "conquerors lived for a long time in a constant state of alert"; elsewhere the lord's wife presided over a separate residence (domus, aula or mansio in Latin) close to the keep, and the donjon was a barracks and headquarters. Gradually, the two functions merged into the same building, and the highest residential storeys had large windows; as a result for many structures, it is difficult to find an appropriate term. The massive internal spaces seen in many surviving donjons can be misleading; they would have been divided into several rooms by light partitions, as in a modern office building. Even in some large castles the great hall was separated only by a partition from the lord's "chamber", his bedroom and to some extent his office.
• Curtain wall
Curtain walls were defensive walls enclosing a bailey. They had to be high enough to make scaling the walls with ladders difficult and thick enough to withstand bombardment from siege engines which, from the 15th century onwards, included artillery. A typical wall could be 3 m (10 ft) thick and 12 m (39 ft) tall, although sizes varied greatly between castles. To protect them from undermining, curtain walls were sometimes given a stone skirt around their bases. Walkways along the tops of the curtain walls allowed defenders to rain missiles on enemies below, and battlements gave them further protection. Curtain walls were studded with towers to allow enfilading fire along the wall. Arrowslits in the walls did not become common in Europe until the 13th century, for fear that they might compromise the wall's strength.