Columbia subject headings:
Fortification--Italy--Syracuse.
Masonry--Italy--Syracuse.
Syracuse (Italy)--Antiquities.
Harvard subject headings:
Fortification, Greek--Italy--Sicily.
Greeks--Italy--Sicily
Sicily (Italy)--Antiquities
Walls--Italy--Sicily.
Princeton subject headings:
Fortification--Italy--Syracuse.
Masonry--Italy--Syracuse.
Syracuse (Italy)--Antiquities.