This is generally a tall defensive tower found in most 12th Century German Medieval castles. They were “free standing” structures, not connected to other defensive structures within a castle or fortifications. They are often mistaken for Keeps or Donjons. The difference is that Berfrieds were not designed for permanent habitation. A typical Bergfried could have up to 6 levels insides (connected by stairs or ladders). They would have few to no windows installed. They were used as watchtowers and as siege “safe houses” designed to safely “wait out” a siege. Any “living quarters” would have been small and uncomfortable. There was no sewage or related water storage. Bergfried Towers were a popular feature used in the building designs of The Teutonic Knights. Constructed of stone,the base of the Tower was wider and heavily reinforced. Although strong, the Tower would lose some of it's strength the higher it was built. In some other designs, the tops of the Bregfried's were made as a fighting platform (to be used by archers and other missile troops). Rarely would catapults or other large siege weapons be installed. Bergfrieds did not catch on in the rest of Europe.