A butter-churn tower (German: Butterfassturm) is a two-part defensive tower in which the upper section has a smaller diameter than the lower section. This design provides a ledge or fighting platform about half-way up that acts as a chemin de ronde whilst the narrower tower that rises from this platform acts as a raised observation point. The two sections of the tower are usually cylindrical, but in rarer cases butter-churn towers may have a square plan. Its name derives from its shape which is similar to that of an upright butter churn: a cylindrical container with a shorter, narrower top section.