The living quarters of a castle with a bergfried are separate, often in a lower tower or an adjacent building called a palas (an English-style keep combines both functions of habitation and defence.)
For maximum protection, the bergfried could be sited on its own in the centre of the castle's inner bailey and totally separate from the enceinte.
In late medieval Low German documents, however, the terms berchfrit, berchvrede and similar variants often appeared in connexion with smaller castles.
There are theories about it being derived from Middle High German or Latin, or even from a Greek word brought back from the Crusades.
[6] A theory that is often stated in older texts, that the bergfried took its name from the phrase "weil er den Frieden berge" ("because it keeps the peace"), i.e. it guaranteed the security of the castle, cannot be confirmed.
However the origin of the design is not fully understood, since towers dating from before the 12th century have had to be almost entirely excavated archaeologically, and only the lowest sections remain.
Towers with triangular and pentagonal floor plans invariably had a corner facing the main line of attack on the castle.
The octagonal bergfried of Gräfenstein Castle can be considered a special case in which plinth on the side facing the line of attack has been extended to form triangle, making the tower heptagonal.
Based on the castles of the Teutonic Order, this type of tower is also common in Central Poland (e.g. Brodnica, Człuchów, Lidzbark Warmiński).
In the last decade of the 20th century there has been discussion in the field of castle research about whether the bergfried's functions could be succinctly stated as a "fortification or (more likely) a status symbol."
With its enormous wall mass - the plinth is even solid in some cases [11] - the tower offered passive protection for the areas of the castle behind it.
For this reason, at many castles the bergfried was situated on the main avenue of attack, often set into the front defensive wall.
That bergfrieds with pentagonal or triangular plans are mostly aligned with a corner facing the main line of attack, is also associated with the shield function: stone projectiles hurled by catapults were deflected laterally by the oblique angle of impact.
In other cases, the acute-angled floor plan is, however, simply due to the natural shape of the bedrock [12] Because the bergfried was the highest building in the castle, it usually functioned as watchtower or observation tower.
Additional chemins de ronde (walkways behind the battlements) could be built on the lower storeys of a tower (e.g. Bischofstein Castle on the Moselle).
In particular, the shaft-like cellars in the base of the tower were often used as a form of dungeon called an oubliette, which was only accessible through a narrow opening in the ceiling.
The thick walls used in the base only left a narrow, about 4-8 metre high, internal space that was usually covered by a stabilizing vault and was only accessible through a hatch at its apex.
Most reports of the incarceration of prisoners in the basement of a bergfried date to the late Middle Ages and early modern period; to what extent this was common before then, is uncertain.
The bergfried in its status symbolism is perhaps comparable to medieval family towers in some northern Italian and German cities, whose sometimes bizarre heights cannot be explained in military terms.
In addition, there were, for example, in Regensburg, no armed conflicts between the urban patrician families, so that here the status function was dominant from the beginning.
Often, the bergfried here the only element here largely retained in its original form from the old medieval castle, which in turn can be regarded as evidence of its role as the (now traditional) symbol of power.
During the schloss building of the Renaissance era (and to a lesser extent the Baroque too) towers again played an important role as elements of a stately home, even if they now mostly had no longer any defensive function (Moritzburg, Meßkirch Castle).
More recent castle research, especially the group around the Bavarian medieval archaeologist Joachim Zeune, has placed in doubt the function of the bergfried as a refuge in case of siege.
Princely territories at that time were protected by a dense network of small and medium-sized fortifications, which was supplemented by the fortified estates of sub-vassals.
Thanks to their solid construction many bergfrieds even escaped later demolition attempts by the surrounding rural population, who wanted to carry off building materials from abandoned castles and reuse them.
A siege was only worth undertaking if the attacker had previously ensured he had legal authority and had asked the state sovereign or even the emperor for permission.
In the Middle Ages in the event of a siege, a massive bergfried was undoubtedly the safest building in which women, the elderly and children could seek refuge during the fighting.
The largest main tower of a medieval European castle, the mighty donjon of the French Château de Coucy, was still viewed as a threat during the First World War.
The German High Command had the roughly 50-metre-high tower blown up on 27 March 1917 in order to cut off the line of retreat for French troops, in spite of widespread international protests.
In the 16th century the Augsburg family of Fugger acquired the Marienburg in Niederalfingen in the present-day county of Ostalb in the German state of Baden-Württemberg.