Columbia subject headings:
Harvard subject headings:
Architecture--Italy--Castel Gandolfo.
Art--Italy--Castel Gandolfo.
Castel Gandolfo (Italy)--Antiquities.
Castel Gandolfo (Italy)--Buildings, structures, etc.
Castel Gandolfo (Italy)--Guidebooks.
Castel Gandolfo (Italy)--History.
Princeton subject headings:
Castel Gandolfo (Italy)--Buildings, structures, etc.
Castel Gandolfo (Italy)--Guidebooks.
Castel Gandolfo (Italy)--History.
Guidebooks.