Columbia subject headings:
Castles--Italy--Pictorial works.
Fortification--Italy--Pictorial works.
Italy--Pictorial works.
Harvard subject headings:
Castles--Italy--Pictorial works.
Fortification--Italy--Pictorial works.
Italy--Pictorial works.
Princeton subject headings:
Castles--Italy--Pictorial works.
Fortification--Italy--Pictorial works.
Italy--Pictorial works.