Columbia subject headings:
Harvard subject headings:
Castel Sant'Elmo (Naples, Italy)
Fortification--Italy--Naples.
Historic buildings--Italy--Naples.
Naples (Italy)--Buildings, structures, etc.
Princeton subject headings:
Castel Sant'Elmo (Naples, Italy)
Fortification--Italy--Naples.
Historic buildings--Italy--Naples.
Naples (Italy)--Buildings, structures, etc.