Columbia subject headings:
Architecture, Medieval--Italy--Gradara.
Castles--Italy.
Fortification--Italy.
Gradara (Italy)--Buildings, structures, etc.
Harvard subject headings:
Fortification--Italy--Gradara.
Gradara (Italy)--History.
Rocca di Gradara (Gradara, Italy)
Princeton subject headings:
Fortification--Italy--Gradara.
Gradara (Italy)--History.
Rocca di Gradara (Gradara, Italy)