Columbia subject headings:
Fortification--Italy--Palermo--History.
Fortification--Italy--Taormina--History.
Military architecture--Italy--Palermo--History.
Military architecture--Italy--Taormina--History.
Harvard subject headings:
Fortification--Italy--Palermo--Design and construction.
Fortification--Italy--Taormina--Design and construction.
Palermo (Italy)--Buildings, structures, etc.
Taormina (Italy)--Buildings, structures, etc.
Princeton subject headings: