- Strong, thick walls: Stone keep castles were built with thick walls, often several meters thick, to provide protection against attack.
- A central keep: The keep was the most important part of the castle, and it was usually located in the center of the castle grounds. The keep was typically a tall, square or rectangular tower, and it served as the lord's living quarters and as a place of refuge in times of attack.
- Arrow slits: Arrow slits were narrow, vertical openings in the castle walls that allowed defenders to shoot arrows at attackers without exposing themselves too much.
- Machicolations: Machicolations were openings in the parapets of the castle walls that allowed defenders to drop rocks, boiling water, or other objects on attackers below.
- A moat: A moat is a deep, wide ditch that surrounds the castle. Moats were used to deter attackers from approaching the castle walls.
- Drawbridges: Drawbridges were used to span the moat and allow people and supplies to enter and exit the castle. Drawbridges could be raised in times of attack to prevent enemies from entering the castle.
- Gatehouses: Gatehouses were fortified structures that protected the castle's main entrance. Gatehouses were often equipped with drawbridges, portcullises, and murder holes.
- Towers: Stone keep castles often had several towers, which provided additional protection and allowed defenders to have a better view of the surrounding area.
