What is crenellations?

Crenellation is a series of indentations or gaps in the parapet or upper portion of a defensive wall or castle, which allowed defenders to fire through them while remaining protected. These indentations can be found along the top of walls, towers, and battlements. The word crenellation comes from the Latin word crena, meaning a notch or a gap. These features can serve both a defensive and decorative purpose, and are often associated with castles and fortifications of the Middle Ages. Crenellations also serve as a visual symbol of power and military might, making them a common architectural feature in medieval Europe and other regions of the world.