This type of stone keep castl soon replaced the Motte and Bailey castles as it offered a better form of defense. A stone keep was the central feature, with thick walls and few windows. Entrance to the keep was by stone steps leading to the first floor. The kitchens were situated on the ground floor while living quarters were on the upper floors. The first keeps were rectangular in shape but later ones were often circular. The Stone Keep would be surrounded by a thick stone wall containing turrets for lookouts.
The Bailey was now the area outside the keep but within the outer walls and shelter for animals or craft workshops might be built against the walls. The entire castle might be surrounded by a ditch or moat and entrance to the castle was by drawbridge.
Foremost for the castle's defense was its keep, a fortified tower built within the castles, used as a refuge of last resort if the castle fell to an enemy. The first keeps were made of wood, and they emerged in Normandy and Anjou during the tenth century. The Normans brought the design with them to England in their 1066 conquest and spread it across the island in a few years; the Domesday Book, a thorough accounting of all England's inventory, mentions hundreds of castles constructed in the wake of the conquest.
In the tenth and eleventh centuries the Anglo-Normans and French began to build stone keeps in square and circular design. Keeps made of stone were considerably stronger against enemy missiles and other offensive weapons, but they took a decade or more to build and could be prohibitively expensive.
Stone keeps took on different design patterns over the centuries. In the twelfth century quatrefoil-shaped keeps were introduced, while England built polygonal towers. Keeps fell out of fashion by the sixteenth century as firearms and cannons made stone defensive fortifications obsolete.