Columbia subject headings:
Castles--Europe--History.
Castles--Italy--History.
Castles--Italy--Lombardy--History.
Harvard subject headings:
Castles--Europe--History.
Castles--Europe--Pictorial works.
Castles--Italy--History.
Castles--Italy--Lombardy--History.
Castles--Italy--Lombardy--Pictorial works.
Castles--Italy--Pictorial works.
Princeton subject headings:
Castles--Europe--History.
Castles--Italy--History.
Castles--Italy--Lombardy--History.