Columbia subject headings:
Architecture, Medieval--Italy--Umbria.
Castles--Italy--Umbria.
Fortification--Italy--Umbria.
Umbria (Italy)--History, Local.
Harvard subject headings:
Castles--Italy--Umbria.
Fortification--Italy--Umbria.
Umbria (Italy)--History.
Princeton subject headings:
Castles--Italy--Umbria.
Fortification--Italy--Umbria.
Umbria (Italy)--History.