Columbia subject headings:
Harvard subject headings:
Fortification--Italy--Portoferraio.
Portoferraio (Italy)--Buildings, structures, etc.
Portoferraio (Italy)--History.
Princeton subject headings:
Fortification--Italy--Portoferraio--Repair and reconstruction--History.
Portoferraio (Italy)--Buildings, structures, etc.--History.