Columbia subject headings:
City walls--Italy--Rome.
Fortification--Italy--Rome.
Rome (Italy)--Buildings, structures, etc.
Rome (Italy)--History.
Harvard subject headings:
City walls--Italy--Rome.
Doorways--Italy--Rome.
Military architecture--Italy--Rome.
Rome (Italy)--Buildings, structures, etc.
Princeton subject headings:
City walls--Italy--Rome.
Fortification--Italy--Rome.
Rome (Italy)--Buildings, structures, etc.
Rome (Italy)--History.