Columbia subject headings:
Castles--Italy--Romagna.
Fortification--Italy--Romagna.
Romagna (Italy)--Description and travel.
Towers--Italy--Romagna.
Harvard subject headings:
Castles--Italy
Romagna (Italy)--Description and travel.
Towers
Princeton subject headings:
Castles--Italy.
Romagna (Italy)--Description and travel.
Towers.