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