Columbia subject headings:
Architecture, Medieval--Italy--Conca River Valley.
Castles--Italy--Conca River Valley.
Castles--Italy--Meleto (Emilia-Romagna)
Fortification--Italy--Conca River Valley.
Harvard subject headings:
Architecture, Medieval--Italy--Conca River Valley.
Castles--Italy--Conca River Valley.
Castles--Italy--Meleto (Emilia-Romagna)
Fortification--Italy--Conca River Valley.
Princeton subject headings: