Bergfried

A bergfried is a tall tower typically found in medieval castles in German-speaking countries and in countries under German influence. Friar describes it as a "free-standing, fighting-tower". Its defensive function is to some extent similar to that of a keep or donjon in English or French castles. However, the characteristic difference between a bergfried and a keep lies in the fact that a bergfried was typically not designed for permanent habitation. The living quarters of a castle with a bergfried are separate, often in a lower tower called a palas. (An English-style keep combines both functions of habitation and defence.) Consequently, a bergfried could be built as a tall slender tower with little internal room or vaults and few if any windows. The bergfried served as a watchtower and as a refuge during sieges (at least if the siege was relatively brief). The distinction between a bergfried and a keep is not always clear-cut, as there were thousands of such towers built with many variations. There are some French keeps with only austere living quarters, while some late bergfrieds in Germany were intended to be habitable (Piper 1900).

For maximum protection, the bergfried could be sited in the centre of the castle ward unconnected to the curtain wall. Alternatively, it could be close to the curtain wall on the most vulnerable side as an additional defence, or even project from the curtain wall. For instance, the Marksburg has its bergfried in the centre, and Burg Katz on the side most likely to be attacked. Some castles, such as Münzenberg castle, have two bergfrieds.

Outside Germany, the crusader castles of Montfort and Judin built by the Teutonic Knights had prominent towers that some authors have compared to a bergfried (Kennedy 2000, Folda 2005), arguing that these castles depended more on Rhineland than local crusader traditions of military architecture.

Eynsford Castle in Kent is a rare English example, where the fighting-tower or bergfried is the central element of the design.

Etymology
The word '"bergfried", sometimes spelled "berchfrit" is cognate with belfry.