zwinger

thumb|Gateway leading into the in Carcassonne. Right: the lower Zwinger wall. thumb|Example of a : the Minneburg in the Odenwald thumb|The around Coburg Fortress reinforced by early modern era bastions

A '''''' () is an open kill zone area between two defensive walls that is used for defensive purposes. s were built in the medieval and early modern periods to improve the defence of castles and town walls. The term is usually left untranslated, but is sometimes rendered as "outer courtyard", presumably referring to the subsequent role of a as a castle's defences became redundant and it was converted into a palace or schloss; however, this belies its original purpose as a form of killing ground for the defence. The word is linked with , "to force", perhaps because the forced an enemy to negotiate it before assaulting the main defensive line. Essenwein states that the "main purpose of this feature was so that the besieging force could not reach the actual castle wall very easily with battering rams or belfries, but had to stop at the lower, outer wall; also that two ranks of archers, behind and above one another, could fire upon the approaching enemy".