A half tower (sometimes half-tower), open tower, or open-gorged tower (German: Schalenturm, Halbschalenturm or Schanzturm) is a fortified stone tower in an external wall or castle enceinte that is open, or only lightly constructed, at the rear. Towers of this type were used, for example, in city walls. City gates can also be incorporated into a type of half tower.
Unlike closed towers, which were fully enclosed by walls, half towers were open on the inside, typically the side facing the city or the inner bailey of a castle. On this side, a wooden railing on individual floors stopped people or objects from falling off. Sometimes the open side was sealed with wooden planking or weaker timber framed walls. Towers that are fully open at the top and rear are 'open towers, whilst those only open on the lower floors (i.e., the top floor is walled and roofed) are partially open towers.
Most half towers were semi-circular in plan, but some were rectangular.
City or town wall towers
Town wall towers in