Defensive element at the stage of evolution between the tower and the bastion, being a low, squat building capable of defending both adjacent sections and front sections. It was built on a circular plan, half circular or polygon with a diameter of several to dozens meters. As a rule, much wider than the higher. Most often it was incorporated into a defensive circuit, sometimes strongly extended from the curtain, in which case it was connected to it by neck. Defense equipment were hand-gun arrowslits and artillery positions on the terrace. It appeared in Italy in the 15th century, due to the spread of firearms.