Occurrence of Attributes in Original Text

The text related to the cultural heritage 'Castel del Monte' has mentioned 'Fortification' in the following places:
Occurrence Sentence Text Source
Italian historian Raffaele Licinio often condemned those esoteric views and interpretations, stressing that Castel del Monte was just one of the castles of the fortification system developed by Frederick II, and it is not in any way linked to the Templars.