Ridge Castles were derived from the German "Kammburg" or Hill Fort. They were Medieval fortifications of different classifications built into ridges, crestlines and mountains. These were NOT common defense designs. Although well protected, their primary weakness was that they could be successfully attacked from two sides. Additionally, the hilltops that they were built, often sloped easily to the ground. Geography permitting, perimeter walls could be built into these outcroppings to help in protection (towers were seldom used). Burghausen Castle in Bavaria is an excellent example of this defense type.