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