A castellanus (or castellatus) (from latin castellanus, castle) is a cloud that displays at least in its upper part cumuliform protuberances having the shape of turrets that give a crenellated aspect. Some of these turrets are higher than they are wide; they have a common base and seem to be arranged in a line. The castellanus characteristic is particularly obvious when the clouds are observed from the side (i.e., from a vantage point on a line perpendicular to the line of orientation).