Murder holes are openings in the ceilings of castle gateways or passageways, designed for defense. They allowed defenders to drop harmful substances, such as boiling oil or stones, onto attackers trying to breach the entrance. This strategic feature helped protect the castle from invaders. Typically found in medieval castles, murder holes were part of a larger defensive system that included features like moats, drawbridges, and arrow slits. Their placement was crucial, as they provided a tactical advantage, allowing defenders to strike from above while remaining relatively safe from direct attack.