Battlement: Battlement refers to the parapet (protective wall) at the top of fortifications that includes alternating low sections called crenels and higher sections called merlons.
Moat: A moat is a deep trench filled with water surrounding a castle or fortress. It acted as an obstacle for attackers trying to breach the walls and provided an additional layer of defense.
Drawbridge: A drawbridge is a bridge that can be raised or lowered to allow or deny access across a moat. It was often used as the main entrance to castles and could be lifted in times of danger.