Columbia subject headings:
Gates--Italy--Sicily--Pictorial works.
Sicily (Italy)--Buildings, structures, etc.--Pictorial works.
Harvard subject headings:
City walls--Italy--Sicily.
Gates--Italy--Sicily--Pictorial works.
Sicily (Italy)--Buildings, structures, etc.--Pictorial works.
Princeton subject headings:
Gates--Italy--Sicily--Pictorial works.
Sicily (Italy)--Buildings, structures, etc.--Pictorial works.